Project Overlord was a great DLC, but it unfortunately had a ton of plot holes and missed opportunities, the most glaring being a complete lack of dialogue for Legion and Tali, whom I felt would be most personally affected by the project in question. What I'm attempting to accomplish with this story is a comprehensive overview of the mission while trying to patch the various holes in the plot that the game did not bother to address.

I am indebted to the Mass Effect wiki for providing background information, as well as to Youtube users cshep25 and Darksydephil (DSPGaming) for allowing me to view Overlord's cutscenes and gameplay together in a very entertaining manner.

On a side note, I am far from a computer security expert, so please forgive any artistic license I may take with the nature of the VI infection. The VI itself was practically magical anyway in the game, so I do hope that whatever I come up with will not break willing suspension of disbelief... too badly.

Chapter 1: Messenger of Hermes

Normandy SR-2, 14 days after Omega-4 mission

"Shepard. I was afraid you weren't going to pick up. I'm glad you did."

"I didn't think you'd be calling back so soon."

The Illusive Man took a moment to take a long drag from his cigarette before pushing it into the ashtray. "I'm not here to talk about your decision regarding the Collector base. What's done is done. Don't get me wrong, I'm not happy about your choice, but I didn't get to where I am by constantly trying to change the past. No, we need to talk about the future."

"Just get to the point."

"About 3 days ago, a Cerberus facility on the planet Aite went completely off the grid. One moment they were fine, the next it's like they completely vanished from the universe. I need you to go there and find out what happened."

Shepard frowned. "I seem to recall from our last conversation that I don't take orders from you anymore. What makes you think I'm going to bother now?"

"Because you're not stupid. You know I wouldn't be calling you if this wasn't something of critical importance. You want to play the wandering hero and fight the good fight, be my guest. As long as you're contributing something to the fight against the Reapers, I'm not going to stand against you." He paused, letting his cybernetic eyes meet Shepard's for a long moment. "This facility was working on a project codenamed Overlord. If something has gone wrong –"

"Another one of your insane science projects?" interrupted Shepard. "When are you going to learn to stop playing with things you can't handle? Forget it, I'm not touching this one."

"– then there may not be a galaxy left for the Reapers to harvest," finished the Illusive Man, his tone not wavering in the slightest. "That, Shepard, is the difference between this project and the others. The previous experiments that regrettably spun out of our control could at least be contained to a planet, or at most a single solar system. Project Overlord has the potential to escape off-world and destroy all galactic civilization as we know it."

"So what were you working on that could possibly do that?"

"I can't say, not even on a channel as secure as this."

"You damn well better throw me a bone here or you can forget about getting my help."

The Illusive Man merely stared at him for a long while before pulling out another cigarette. As Shepard waited, the head of Cerberus calmly lit up and took another drag before meeting his eyes again.

"Geth."

Shepard's eyes narrowed at the admission. "Geth? What were you trying to do? You realize with Legion on board, this may have destroyed any chances we have to negotiate with them?"

"That's exactly why you need to fix this situation up, and fast. This project began long before we had any idea what your pet geth told us about them. And that's all I dare say about Overlord. Get to planet Aite, find out what happened, and salvage what you can. I'm sending coordinates to EDI now." With those words, the real-time communication cut off. Light flooded Shepard's vision and he was back in the Normandy's briefing room.

Tali'Zorah vas Normandy stepped away from her position where she'd been leaning against the wall and caught his gaze. "I don't like this, Shepard. This doesn't sound good at all."

He sighed. "You don't need to tell me that. Everything about this is rotten from the start. But at the same time, it says a lot about the seriousness of this situation that the Illusive Man would actually bother to contact me in person, especially after I basically turned in my resignation letter at the Collector base. I guess you wouldn't know since this is the first time you've seen and heard him, but he was agitated. Considering all the times I've talked to him, if something could make him nervous, this must be big."

"You have a point there," she muttered as they turned to exit the briefing room. "Still, geth? I thought Cerberus couldn't get any lower after everything they've done, and they still manage to surprise me."

"Tell me about it," he said. "So," he turned to her. "Can I count on you to back me up down there?"

"Of course you can," she said.

They turned to their left and entered the armory, where Jacob was finishing up repairs on some of their equipment. "Jacob," said Shepard by way of greeting as he clapped a hand to the other man's arm. "How's everything going?"

"Well enough, Commander," said Jacob as he started to reassemble the submachine gun he was working on. "Still working on fixing up some of the kinks our equipment took on the Collector base, but I should be done with that soon."

"Are my weapons ready? Sounds like we've got geth to deal with."

"Geth?" asked the armory officer. Shepard took a moment to give him the short version of the conversation. When he was finished, Jacob simply shook his head in disbelief.

"What is that man up to now?" he muttered. "Well, to answer your question, I fixed the jamming problem in your submachine gun, boss. Not to mention I finally had a chance to apply some of those schematics we found in the Collector base; your handgun should pack a hell of a punch now.

"Thanks, Jacob," he said.

"Anytime. Drop by and pick them up once we get to Aite."

Aite was a beautiful world, a veritable garden planet in the Phoenix Massing. From the files that Shepard had acquired, though, it was a trap: the planet was due for a stellar collision in less than 200 years. In the meantime, until that happened, lawless bands of settlers, primarily human and batarian, were determined to eke out a living on Aite until the end came for the world.

"Geez, Commander, how many times now has a Cerberus science project blown up in their face?" asked Joker as the planet came into view.

"My thoughts exactly Joker. You know there's something the Illusive Man isn't telling me that's gonna bite me in the ass when we land. Anyway, have you found the facility yet?"

"A scan of the relevant sector has located the building. It appears to be spread out over an area of several tens of miles. Recommend a ground transport to fully investigate the entire area," said EDI.

"Thanks EDI, but I was about to use the scanner myself," complained Joker.

"It is only fair that I get my share as well," deadpanned the AI.

"You two are worse than an old married couple," muttered Shepard as he turned back to the CIC. "Looks like we'll need some ground transport to cover the whole area." He touched the communicator on his earpiece. "Garrus, is the Hammerhead ready for action?"

"It's ready to roll out boss," replied the turian. "Engine is purring like new but I didn't exactly have time to finish the calibrations on the cannon."

"You would never finish those calibrations even if you had a hundred years to do it. We'll make do for now." He hit the elevator call button as Tali fell into step beside him and waited.

"Shepard-Commander."

They both turned in the direction of the monotone voice that had appeared at their side. "Yes, Legion? Is everything set on your end?" asked Shepard. He had already briefed the synthetic on the mission and it had agreed to accompany him and Tali as part of the primary fireteam.

"Yes. We will acquire our weapons from Crewman-Taylor."

"While you're at it, could you retrieve our weapons as well? We'll be waiting for you at the Hammerhead."

"Acknowledged." And with that, the synthetic walked away as the two organics stepped into the elevator.

The elevator began to move as Shepard turned to Tali. "I know you don't like it, but –"

"I'll be fine," she cut him off abruptly. "It has a point, and we could use its abilities if we do end up fighting other geth. I just don't want to be alone with it. Not even after everything we've been through."

"You won't. You handled yourself just fine when we went with it to eliminate the heretics and I know you'll do fine here. I know it's difficult to have to work with a being you've been raised and trained to hate, but all things considered, I think you're adjusting quite well."

She smiled at those words. Somehow Shepard always found a way to make her feel better about herself even in her worst moments. "Thank you… Captain."

"You're welcome." He frowned as he looked at the floor indicator. "This elevator takes way too long."

"All right, Commander, we're approaching optimal drop distance," said Joker into Shepard's earpiece. "One minute."

The Normandy's lower hangar doors opened revealing the hovertank and the two Kodiak shuttles with the rest of Shepard's ground crew preparing to launch. Just as the Hammerhead accelerated and was in freefall, the frigate suddenly shuddered.

"What was that, Joker?"

"Not sure!" called the pilot. "I've got weird readings across our consoles. EDI, what's going on?"

"A foreign presence is attempting to overwrite my control of the ship," said the AI's cool voice. "That jolt was me rerouting power from the engine to fry some of the consoles it had compromised. Fortunately they were nonessential. I have put up firewalls to prevent further intrusion but I recommend we immediately get to orbit out of radio transmission range and shut down communications."

"Commander, what do we do?" asked Joker.

Shepard considered the facts for a split second. Cerberus experiments on geth. A foreign intelligence attempting to commandeer the Normandy. An entire research station gone dark. He glanced at Tali and caught her eye. She nodded. He knew she was thinking the same thing.

"Joker, do what EDI said. Team, do not launch the shuttles. Stay on standby until further notice. Once you get back to orbit, do not attempt to initiate communications with us unless I preface the phrase with olly-olly oxen free. If you don't hear back from us in 24 hours, get out of here and alert the Alliance about this planet."

Joker was silent for a moment before replying, "Acknowledged, Commander. Good luck down there."

The Hammerhead rocked as Shepard hit the retro-rockets to slow the vehicle down as it approached the optimal distance to land. A few seconds later, the hovertank touched down and landed in the middle of an empty landing pad as the frigate took off and made for orbit. The main hub of the Cerberus facility was right in front of them. The trio stepped out of the vehicle and looked around, but there was nobody to be found.

"Olly-olly oxen free?" questioned Tali. "Sounds cute."

"It gets the job done just fine," muttered Shepard. "Anyway, eyes up front and stay sharp, both of you," he ordered as he drew his submachine gun and affixed his helmet on top of his N7 armor. "I have no idea what happened here but since we've got a possible geth attack, be ready for anti-synthetic combat."

Tali unslung her shotgun and pumped a round in, then sighted down the barrel. "Got it," she acknowledged.

"Acknowledged," said Legion as it too unfolded its sniper rifle.

They moved at a steady trot through the front door of the facility. Immediately they were greeted with the signs of carnage and death. Two human bodies lay at the end of the lobby in pools of blood while destroyed computers and screens were everywhere.

"Keelah," whispered Tali in horror.

"Analysis: energy burns on walls consistent with geth pulse rifles," said Legion as it continued scanning the room with its optical unit.

"And these people were killed by what looks like an explosive at close proximity," muttered Shepard as he inspected the two dead bodies. "Let's move past this lobby, and watch out for enemy geth."

"Over here!" called an unknown voice.

"What was that?" snapped Shepard as he dropped into a crouch and swept the room, Tali following suit.

"Over here, on the monitor," repeated the faint British voice. Shepard looked and saw a monitor on a table with an image of a scientist waving at the screen. The man was middle-aged, with a thin beard and goatee, a dark receding hairline, and wearing a standard Cerberus scientist uniform. Shepard cautiously edged closer.

"Thank God you came. I'm Gavin Archer, project director of this facility. I've locked myself in a computer room on the other side of the building. There are geth all over the area. A rogue VI has taken control of the facility's systems and is attempting to upload itself off-planet. You need to shut down the satellite communications dish to ensure that it doesn't. An omni-tool should suffice for the task."

Shepard took a look at Tali, who simply shrugged. Turning back to the monitor, he said, "Hold on, slow down. What do you mean a 'rogue VI?' What does that have to do with geth? For that matter, how the hell did you get your hands on geth to experiment with?"

Archer raised his hands in apology. "I'm sorry, but I cannot keep this channel open much longer. The VI may detect it and shut it down. Explanations will have to wait. For now, hurry and shut down the communications dish. The control room is just a few doors away. You should be clear of geth in that area."

The image cut off. Shepard turned to his team and frowned. "All right, you two. Thoughts?"

"This is only going to be a wild guess, Shepard, but I'm thinking that this VI he mentioned is in charge of the geth here," offered Tali. "But that doesn't answer the question of where the geth came from, or what this VI is trying to do."

"We tentatively concur with Creator-Tali'Zorah's assessment. Additional data will be required to derive new conclusions."

Shepard nodded curtly and then gestured for the team to move on. Moving through the facility yielded little else than dead bodies and destroyed computers. They paused for a moment upon entering what used to be a waiting room with a pair of men who had been gunned down. At the same time, what would have been a relaxing classical piano piece continued to drone on over the PA system.

"I've never heard this kind of music before," said Tali, "but it feels very out of place here."

"It's from a piano, human instrument. And yeah, I'm glad to see I'm not the only one unnerved by this."

A few rooms later, they found the dish control panel. As instructed by Archer, Shepard moved to sync his omni-tool with the controls to retract the dish. The massive instrument began to lower itself.

A horrific screeching noise suddenly erupted out of every speaker in the PA system. It was as if a turian had tried to drag its claws along a starship's hull and then did some sound editing on it as a kind of extranet prank. For Shepard, the effect was far worse. It was as his brain was on fire and his muscles spasming. His omni-tool's glow began to flicker between orange and green.

"Shepard!" cried out Tali as she moved to support him before he collapsed.

"Alert: hacking attempts detected. Rerouting processes to counter-hacking measures. Creator-Tali'Zorah, recommend immediate shutdown of Shepard-Commander's omni-tool."

She didn't have to be told twice. Tali quickly shut it off. Shepard went limp and collapsed, his breath coming in heavily.

"Legion, what happened?" demanded Tali.

The synthetic was silent for a good 10 seconds as its head flaps continued to flutter open and closed. Finally it turned its Cyclops gaze to her. "Upon interfacing of Shepard-Commander's omni-tool with the satellite controls, this platform detected an unknown cybernetic intelligence attempting to install malicious code within us and also within Shepard-Commander's omni-tool. We believe this was the rogue VI that Scientist-Archer warned about. We are currently running a system diagnostic to ensure malicious code was not successfully installed."

"I'm all right," groaned Shepard as he got back to his feet. "Just give me a moment to shake off this damn headache. Legion, what the hell happened to me?"

"Virtual intelligence attempted to interface with Shepard-Commander. It may have been attempting to take control of Shepard-Commander by overriding cybernetic implants with its own initiatives."

For a long moment, Shepard was stunned at the revelation. Then he turned slowly to Tali. "Tali, refresh my memory: you have implants as well, right?"

"Yes. I know what you're going to say, Shepard, don't worry: I'm not going to turn on my omni-tool."

"Precaution unnecessary," said Legion as it continued its analysis. "Creator-Tali'Zorah's implants are not mutually linked together as extensively as Shepard-Commander's. Any override attempt similar to the one initiated upon Shepard-Commander will be unable to physically affect her in any significant manner. In addition, they are not computerized in nature. Creator-Tali'Zorah may use her omni-tool safely."

"Good," breathed Shepard as he turned to look out the window. "What the hell has Cerberus gotten itself into now?"

"Hello? Hello? Are you there?" The voice of Gavin Archer spoke up again from the ceiling speakers. "Damn it. The VI has interrupted the shutdown of the dish. You'll need to destroy the dish manually. There is a tram nearby that will lead you to it. Hurry, there's not much time. I have to shut down this channel now, but be careful: the VI knows you're here."

"Hold on!" yelled Shepard, to no avail as the channel shut down. "When I meet this guy, remind me to beat the crap out of him after we've gotten our answers."

"You and me both, Captain," muttered Tali as she shouldered her shotgun. "Let's go."

They moved on to the next room, what was clearly a dining area for the staff of the facility. Unlike before, the place was pristine, with no dead bodies or signs of carnage. Shepard and Tali moved to a raised platform that overlooked the area and took a moment to survey the large room.

"Shepard-Commander! Movement detected! Take cover!"

At Legion's agitated command, Shepard grabbed Tali's arm and pulled her down with him behind the bullet-proof glass of the platform's safety rail. Less than a second later, a rocket went flying over their heads and impacted the wall behind, spraying bits of plaster and concrete around. Shepard looked up and saw their attacker, a geth rocket platform on the second story accompanied by another unit of the same design. From the kitchen, multiple geth troopers were pouring out, pulse rifles blazing. Legion moved to crouch next to the two.

"Dammit! Tali, use your combat drone and try and distract them for a bit. Legion, I'm going to move up and get to that pillar in the center of the room. Give me sniper support."

"Got it!" said Tali as she summoned her drone. "Go get them Chiktikka."

The glowing blue orb materialized and moved to zap the closest geth. At the same instant, Shepard vaulted over the railing and laid in a burst of fire at a geth destroyer that had come out of the kitchen. The two geth rocket troopers on the second floor were eliminated by a volley from Legion's anti-materiel rifle.

"Tali, move on, I've got them suppressed!"

She moved to follow his lead, vaulting over the rail and dashing up to the window that separated the dining area and the kitchen. A geth trooper was still in the kitchen until she stood up and put a shotgun blast through its optic.

"All right, Legion, move up with me into the kitchen." Shepard disengaged from the pillar and leapt into the kitchen, quickly moving to take up position by the side door that led to an antechamber near the tram. Another group of geth was coming up from the tram station. A shielded geth destroyer led the way, but a tech overload from Shepard collapsed it and cleared the way for Tali to put a volley of shotgun blasts into its midsection before it could engage its flamethrowers, leaving it a pile of scrap. Legion's AMR barked another three times, and the remaining geth fell.

"I think that's all of them. Everyone OK?"

"I'm fine, Shepard. Nothing got past my shields."

"No damage detected."

"Something's up here," frowned Shepard. "These geth were a lot easier to deal with than any others I've fought before. I've seen new marine recruits shoot better than they did."

"Maybe it has to do with the nature of the VI controlling them," offered Tali. "I noticed that all the geth units had a green code to them. It's probably not meant for combat."

"Maybe. Legion, any thoughts?"

"We have not needed to send out any form of junk data to impair enemy combat effectiveness. These geth runtimes are scattered and fragmented. They are not linked together in any form of coherent manner."

"That might explain their crappy shooting, but where did they come from, Legion? And what about you? I noticed you too were taking a lot more shots than necessary to put down the enemy."

At that observation, Tali's head snapped over to look at Shepard. "Legion, are you absolutely certain you are not vulnerable to being hacked? Because if you end up turning on us like these other geth…"

"Tali…" warned Shepard.

The synthetic turned to stare at the quarian. "Acknowledged, Creator-Tali'Zorah. This platform wishes for the continued safety of both you and Shepard-Commander. It is exceedingly unlikely this platform will be able to be successfully hacked in the manner as those geth that have already attacked. However, a successful hack attempt still has a positive non-zero probability of success. To ensure additional precautions against a hacking attempt, in addition to shutting down wireless communications, we can partition our runtimes so that any successful hack attempt will only gain control of selected mobility functions instead of the entire platform. Addendum: partitioning runtimes will reduce processing power and may impact combat capability. Requesting recommendation from Shepard-Commander."

Instead of answering, Shepard turned to regard his engineer. "Well, Tali, I'd like to hear your opinion on this too."

She took a moment to answer. "This whole situation is already terrible, Shepard. I don't think we need to worry about an… ally turning its guns on us. If the enemies we're facing don't get much worse than what we've already fought, then I think we can handle it even if Legion has to shoot like a child getting his first gun."

"All right, Legion. Go ahead and partition yourself off. We can't afford to take any chances."

"Acknowledged."

The three of them then moved out to the tram to the communications dish. The ride was largely uneventful, if a bit slow. During the ride Legion announced it had finished its partitions and they stepped out to their destination. The dish was suspended above a tall canyon, service catwalks being the only way into the superstructure.

"Ugh…" moaned Tali as they traversed the catwalks near the dish.

Shepard glanced back at her. "You all right, Tali?"

"I don't know, it's just… well, on the Flotilla, there's no such thing as being high up. I guess I'd better not look down," she admitted.

"Vertigo," said Shepard. "Sounds like a good idea, just keep your eyes on me."

She muttered something back in Khelish that his translator didn't quite catch, the hint of a smile in her tone. He fought down the smirk that threatened to appear.

They came to a gap in the catwalk, which Shepard quickly remedied by toggling a switch to extend a bridge. As they were walking, movement at the corner of her eye caught Tali's attention.

"Catwalk across from us, enemy targets!"

A volley of fire came from the three geth platforms. Shepard and Tali quickly ducked behind the railing and moved to pull out their heavy pistols. At the same time, Legion's AMR thundered as it returned fire.

Tali stood up and emptied her clip at a geth trooper that was spraying in their direction. A few shots impacted on her shields, but the trooper she was aiming at took a hit in the optical unit and collapsed, falling off the catwalk as Shepard took out another trooper in a similar manner. The final geth trooper's head exploded as a massive AMR bullet tore through it.

"Well, I don't think Legion's targeting capabilities are that bad," said Shepard as he handed Tali another thermal clip. "I think we're just so used to Legion rarely missing that when it starts shooting like an organic sniper, our standards get skewed."

"Glad to hear it," said Tali as she reloaded her weapon and stowed it in favor of her shotgun. "Anyway, let's hurry this up."

The interior of the satellite dish was large yet empty. Shepard gave Tali a questioning look as they ascended up to the roof of the dish.

"Heavy armor units present!" called out Legion as all three dove behind cover. A barrage of pulse blasts and rockets flew over their heads. Tali risked a quick glance at their opposition and let out a curse in Khelish as a missile impacted against her and threw her to the ground.

"Tali!" called Shepard as he quickly pulled her closer to cover. "You all right?"

"I'm fine," she hissed as she leveraged herself to a more comfortable crouch. "Just weakened my shields. Anyway, we have three Geth Primes up ahead, Shepard. This isn't going to be easy."

"Damn it. We'd better focus on one at a time. I'll head to the right and draw their fire. I'll need you and Legion to give me suppressive fire as I do so. Use your combat drones and drain their shields. As soon as that's done, do you think you can hack them?"

"We are tasked to maximum capacity on limited runtimes," said Legion. "An AI hack on heavy armor platforms will be likely to fail."

"I'll handle the hacking," said Tali. "Go get them, Captain."

Shepard nodded and vaulted over their cover. He immediately broke into a sprint while taking a few potshots at the enemy geth as Legion's AMR fired. The barrage of pulse fire sparked off his shields as he dove behind another slab of cover. At the same instant, a pair of combat drones materialized and moved to harass the center Geth Prime. Unsure of how to deal with the new threat, the other two began to fire upon the drones, easing up the pressure on Shepard. He stood up and launched an overload mine at the center Prime. It sparked and froze for a moment as its shields collapsed.

Taking her cue, Tali activated her omni-tool and set up a wireless connection with the shieldless Prime. Years of experience in writing code enabled her to effortlessly bypass the VI programming and replace it with her own malicious code. The hacked Prime turned its weapons on its comrade to the left. Upon seeing the result, Shepard stood and emptied his SMG into the vulnerable Prime as Legion and Tali did the same with their weapons.

In seconds, the Prime on the left had fallen. Tail's hacked Prime, however, was already beginning to system restore itself and overwrite the malicious code. Before it could do so, another burst of SMG fire, coupled with more oversized slugs from Legion's Widow, punched through the Prime's central processor and it collapsed.

With just one Prime left, it proved to be little threat as Tali drained its shields and Shepard and Legion put a burst of fire into its head. Just for good measure, upon collapsing, Shepard moved and smashed its head with his boot.

"I think that's it," he said as he ejected his spent thermal clip and slapped in a replacement. "Legion, can you offer any explanation as to where these geth came from?"

"We have detected traces of code that are similar to heretic runtimes. However, this is impossible to verify. Enemy geth programs have been heavily overwritten by unusual programming patterns that we do not recognize. It is possible these geth were a heretic force that had ventured beyond the Perseus Veil, but we do not know how Cerberus was able to gain control of them."

"Never mind that. We need to destroy this dish. I see three support structures that are holding this up. If we take out the power regulators at each base, we should at least render it inoperable. Everybody take one."

Minutes later, all three regulators were scrap. What Shepard had not been expecting was for the unregulated power to start a chain reaction that eventually culminated in a massive explosion with the main dish tipping over.

"You've got to be kidding me…" he muttered. "Everybody off this dish! Jump back down to the catwalk!"

The three of them ran and leapt off the platform just as the main body of the dish collapsed and turned most of the structure into so much junk plummeting into the chasm below. Legion was the first to hit the landing, stumbling awkwardly before it corrected its stance and straightened up. Shepard landed hard on the catwalk as his knees buckled and rolled. An instant later, a heavy weight crashed onto his chest and he let out a whoof of air. That was probably going to leave a bruise.

"Um, sorry," said Tali as she quickly moved to get off of him.

She helped him up to his feet and dusted herself off. "You could have stayed, you know," said Shepard. "I mean, it's not like I'm not used to having you curled up against me."

"Stop that, you bosh'tet." He chuckled, it was so easy to hear the smile in her voice. They had just managed to get their bearings before a call from Legion broke out.

"Shepard-Commander! Incoming organic lifeform!"

"Commander!" called a familiar British voice. Shepard relaxed and lowered his weapon as he saw the figure of Gavin Archer approaching. "I left my room as soon as I heard the explosions. You've done it. But this nightmare is far from over."

Shepard cut him off as he gestured angrily at the ruined dish. "You owe us an explanation. Where did these geth come from? What the hell was Cerberus doing here?"

The scientist turned to gaze into the sky for a long moment before quietly replying, "Man's reach exceeding his grasp."

Next chapter: Fires of Vulcan…