That fateful Halloween, many things happened. Willow discovered what it was like to be a ghost, Buffy discovered that Angel liked her best as she was and all of them discovered that Giles had once been very scary. As for Xander… what he discovered, no one knew, because he claimed he didn't remember a thing.

There was something about the all too innocent tone of his voice and the slightly drawn look to his face that suggested he was lying, but everyone was too relieved that he was all right to press the point. The only indication of anything different was that he seemed to have toughened up slightly, barely noticeably, and fought with rather more grace and skill. That and the fact that his eyes went gold briefly whenever he got seriously angry.

And there was an air about him, which Buffy, Giles, Angel, Oz after his transformation and Willow, as her powers developed, began to feel. A vibe of something incredibly dangerous, a wild power barely in check. If Xander's parents had been talkative, they would have mentioned how often he woke up screaming.

Even Spike avoided antagonising him thereafter, preferring to keep half an eye on him at all times, and Angelus eyed him like he was a time bomb that the Master Vampire would enjoy setting off. Preferably from a distance of several thousand miles away.

Drusilla was fascinated with him, babbling about 'the one who sees is become the golden watchman, but Miss Edith knows he doesn't want to release the dark one'. Xander had given her a look with more than a little golden power in it, and she'd backed down, uncharacteristically silent.

When he'd found out that Joyce had kicked Buffy out of the house, Joyce swore that his eyes had burned a furious golden colour, and that he had gripped the sideboard so hard that his knuckles were completely white. He had said, "How could you?" Then turned and left, slamming the door hard. Later, Joyce noticed several finger shaped dents in the sideboard.

Faith had been drawn to him like a moth to a flame, and when she'd gone bad and tried to rape and kill him, Angel had come in, ready to play the hero, only to find a Faith shaped hole in the wall and a scared looking Xander hugging his knees on the bed.

At the time they had put it down to trauma, but the fact that Faith stayed a very long way away from him after that suggested something else was at work. But if there was, Xander was decidedly cagey about it, and no one felt like pushing someone who looked disturbingly like a wolf at bay. Giles theorised that Halloween had released and integrated the remnants of the Primal Hyena spirit into Xander, which would explain the bursts of strength and the occasionally gold eyes, and his desire not to talk much about it.

When the Mayor had ascended, he declared that something smelled strange, and powerful , about Xander. It might have been the Scoobies collective imagination, but they thought he'd look a little frightened.

Later, Buffy reported incredible power, even more than she had expected, flowing through her when she fought Adam. Certainly, she hadn't expected to be able to throw Adam across the room to make a large dent in the opposite wall with one relatively light punch. She hadn't noticed Xander's sad smile, nor put much on his look of utter torment and terror after the First Slayer decided that she was declaring open season on their dreams.

When Glory came to town, Xander became introspective, and was occasionally heard arguing with himself. About what no one knew. Finally, when Glory took Dawn, Xander walked into the Magic Box and handed Giles a couple of comics and a yellow costume with a blue cape.

"That's what I wore on Halloween. It's who I am."

He said nothing more, just turned and left, kissing Anya briefly, then arranging his face into a grim expression, he went to get ready for the showdown.

Giles read the comics, re read them, then, most uncharacteristically, began to cry. He wouldn't tell Anya what it was, but he grieved for the boy whose little remaining innocence had been stolen by a chaos mage who had shoved the memories of tortured and insane man with earth shattering power into his head. Just for a good laugh. He vowed to make Ethan feel pain. Lots of it.

As Buffy outlined their plan of battle, no one interrupted until she mentioned the part where she would be dealing with Glory. Anya provided the Dagon sphere and pointed out the uses of the Troll hammer. Then Xander spoke.

"I'll deal with Glory. You get Dawn."

"Xander, are you out of your mind?! She'll kill you in, like, ten seconds, even with Willow's reverse brain suckage!" Buffy said incredulously. Everyone else, Giles aside, looked at him as if he had gone mad.

Xander just looked at her levelly, then flicked his gaze to Giles who cleared his throat and said, "Buffy. He's right. Xander's tapped into a strength that would give even Glory pause." He paused, made sure he had everyone's attention, and said, "Even if she was ruler of her Hell Dimension once more."

Buffy's jaw dropped, then she thought for a moment, and shut her mouth. "This is about the gold eyes isn't it," she said quietly. It was not a question, just a statement. Giles nodded.

"On Halloween, Xander became a superhero. One called 'The Sentry'," Giles said, looking to Xander to confirm.

Xander nodded and added, "Think Superman on steroids. And more mental problems than the Joker."

Buffy blinked. Well, that answered her question about why he hadn't used it before. He was scared. Scared of his own power. Suddenly, the state he had been in when Angel found him before Graduation made sense. He hadn't been scared of Faith, he had been scared about what he might have done to Faith. She looked around the room and saw everyone else reach the same conclusions she had.

In a low voice, Xander began to explain the dual nature of the Sentry and the Void. The god complex of Robert Reynolds, and the role of the Sentry in the Fall of Asgard. The casualty figures of the Void's attacks. The desperate measures taken to try and keep it in check. The cataclysmic effect of the failure of those measures.

"I'm scared of this power guys, I'm terrified. I don't know what it'll turn me into. That Halloween, I flew into the heart of the Sun itself to try and get away from my fear." He looked around at them softly, not including Spike, and said, "It was the thought of you guys that brought me back." Then his voice hardened. "I'm going to kill Glory. Not beat her. Kill her, and throw her body into the Sun. Then I'm going. I'm going to see the Universe. To find out who I am and what I've become. Maybe I can get this power under control, use it for what's right. Maybe."

He turned to look at a dismayed looking Anya, and said quietly, "I'm sorry, I'm so sorry. But no matter how much I love you, I can't risk the Void on Earth, especially where there's no one else able to contain it. I love you, and I swear that I will do my best to come back someday."

Anya just nodded, tears in her eyes, and he kissed her gently. No one said anything, and even Spike didn't make a snarky comment. Of course, that was partially to do with the fact that Xander could vaporise him with a thought. But only partially.

That night, faces were grim as they followed Tara to the ramshackle tower, built by the mad for a madder God.

Willow drained Glory's sanity into Tara, then Xander stepped forward. Glory frowned.

"Who are you? I was expecting the Slayer." Then she shrugged, and said as she ran forward, not a blur but still very fast, "I need a snack anyway."

She was deeply surprised when a strong hand caught her by the throat and lifted her into the air as if she weighed no more than a piece of paper. She looked down into a pair of glowing gold eyes and got the sudden sensation that she had bitten off far more than she could chew.

"Glorificus. You don't know what it is to be a god. You take the easy path, and just take, take, take from everyone around you, using and abusing your power," Xander said coldly, then pulled her close and hissed, "I know what it's like to give in to evil. I know how good it feels, just… letting go. But I have a conscience. Friends. These are the fetters that bind me, and the bulwarks that support me. And I'm going to kill you for hurting them."

Glory managed to escape the crushing grasp, punched him hard, sending him flying backwards, and said mockingly, "So you know what it is to be a god, insect? I don't think so. You're strong, I'll give you that but nothing compared to m-"

She was cut off as Xander blurred to within punching range and hit her with a blow that would have crushed several trucks. As it was, she went sailing away, and Xander took to the skies after her.

As Glory struggled out of the rubble of what had once been a convenience store, she knew that she was facing something that was both much stronger than she was. And it was very angry. This was borne out by the figure that was now glowing, glaring and hovering all at once.

"Where did you learn that trick, insect?"

"Chaos Mage. He decided it would be funny to turn me into a man with the power of a million exploding suns for a night. It stuck," Xander said curtly, before lifting her up and throwing her like a dart several thousand feet in the air. As she fell, she was not scared of the fall itself, but unnerved by the ease with which her opponent had thrown her. Then she screamed. Because Xander Harris, the new Sentry, was diving at her from above with murderous intent. The impact left a crater half a mile wide in the Sunnydale desert.

Glory wheezed and twitched. The impact had nearly driven her back to her mortal form. She was bruised, battered, broken and bleeding and on the edge of defeat, but her opponent didn't even look particularly ruffled.

She gasped as he lifted her up with one hand, eyes no longer glowing, and looking weary, but cold. Not in the physical sense, as she sensed he could have fought her all night with one hand, but in the mental sense. He said nothing as he flew her into space. He said nothing as he looked into her eyes then hurled her into the sun. She would have screamed, but no sound travels in a vacuum. And as she burned, looking into those cold eyes, made for laughter but with no humour left in them, she realised that messing with the Slayer and her family would be something that no demon was likely to do anytime soon. As her physical form was obliterated, those eyes never left her, watching as she died.

Xander flew back to earth, for long enough to say that he was alive and Glory was gone. Then, kissing Anya once more, he set out for the depths of space.

The Trio were plotting. As they did so, writing ideas on the whiteboard of evil, the door to their basement exploded. Out of the dust strode a very angry looking Xander Harris, eyes aglow. Jonathan summarised the situation concisely.

"We're fucked."

"I think I just wet myself," Andrew said nervously, and Warren shuffled away from him.

"You know, when I come back from exploring the universe, right at the top of the list of things I don't want to hear is that some Big Bad wannabes have been messing with Buffy," Xander said conversationally, tone belying his expression which was just this side of homicidal.

"Exploring the universe?" Warren asked, scenting an opportunity. "Well, we, that is the Trio, can help you with dealing with your knowledge. We're really good listeners."

Xander chuckled darkly. "The things I could tell you would melt your brain. I fought in the last Great Time War, side by side with Time Lord Generals. I destroyed half the enemy Fleet before they used an emergency temporal shift to escape. I looked into the Eye of Harmony, I flew through it to another universe and I saw things you couldn't comprehend. And that's all I'm saying."

"Ok, let's say we believe what you're saying," Warren said carefully, recognising that no matter how insane or delusional this man might be, he had just blasted through their steel door like it wasn't there. And there was something in his voice that suggested he might be telling the truth. "Who are you?"

"Name's Xander Harris. A name you're more likely to recognise is one I gained after a run in with a chaos sorcerer one Halloween," Xander was slightly pleased to note that Jonathan had just gone extremely pale, and Xander said, "Would you like to say, Jonathan? You look like you know."

And indeed Jonathan did. Despite his naivety in working with the Trio, Jonathan was a smart boy, and tended to think faster when his life was in danger, and with the help of his vast comic knowledge, he'd been connecting a lot of dots.

Fact, four years ago, a powerful Chaos mage had transformed everyone into their costumes. Fact, the effects had occasionally lingered, as Jonathan going as a Jedi had clued him into his magic. Fact, Xander had been at least as geeky as him, at least once upon a time, so would have gone as some comic book character. Fact, Jonathan was pretty certain only a few comics characters could survive something like flying to another universe and whatever a Time War was, and even fewer of them had eyes that glowed with yellow light every now and then, and even fewer could, according to rumour kill a HellGod in hand to hand combat. Or throw her into the sun.

"Guys… Xander's the Sentry," Jonathan said. Andrew looked like he was on the verge of a heart attack or a nerdgasm, and Warren just looked outright terrified at Xander's suddenly shark like smile, which was really unnerving since Jonathan had known him since just after Kindergarten.

"It's so nice to be recognised," Xander said, grinning a grin with far too many teeth in it. "Now. Whose head should I tear off first?"

"Please, have mercy on us!" Andrew wailed, and Warren pushed Jonathan forward, bowing and saying, "accept this sign of our penitence o mighty one."

"Jonathan's the only one worth spit among you lot, so I'll spare him. Andrew's weak and just follows the leader meaning he's not worth killing…" Xander said, then his eyes lit upon Warren, ignoring Andrew's indignant protests, "that leaves Warren. Murderer, attempted murderer, thief, and probably a rapist or an attempted rapist if you aren't building robots any more. Tell me, why should I spare you?"

"Because I can be better, because I can make a better life if you let me live, please!" Warren begged, inwardly thinking that he needed those orbs as soon as possible.

Xander examined him for a moment, then grabbed Jonathan and flew out.

When he arrived back at the Casa del Summers, he noticed something was wrong. Spike's coat was on the banister and there was a bruise on Buffy's leg. And she was still weak from the patrol she had come in from when he got back, and she'd told Xander about her sleeping with Spike. He'd accepted it, mostly because Anya was attempting to drag him away for reunion sex, and along with Willow descending into Magical drug abuse, Dawn's kleptomania, the rise of the Trio and the other problems that had beset the Scoobies since he'd left, and the reunions, tearful and otherwise, he was a bit deluged.

"Xander?" Buffy said, seeing his hair bleached literally white with fury.

"Where?" he hissed.

"What's Jonathan doing here?"

"Information," Xander said curtly, dropping the terrified petty wizard on the couch. "Now where is that no good rapist vampire?"

Buffy shrugged helplessly, not bothering to ask how Xander knew, and said, "He just ran away all of a sudden."

Xander disappeared. A few moments later, a crypt sitting Clem got the fright of his life when the door of the crypt exploded and a glowing Xander floated in.

"Spike. Where?"

Clem, realising he was not the object of Xander's wrath (and feeling a little sorry for Spike), said, "He left for a while. Said he wanted to make things change," as the sentence finished, Xander was gone.

Spike was gunning his motorbike, when he looked down at Sunnydale and saw a rising yellow light. If a vampire's blood could get any colder, his would have frozen. Goldenboy was back in town, and it looked like he had heard of Spike's… misdemeanour. Spike turned off the bike and got off. There was no point in trying to outrun someone who could fly faster than light if he so wished. Especially if said person wanted to obliterate him. The light was closing fast and was beside him less than ten seconds after he'd dismounted.

"Explain in five words or less why I shouldn't destroy you," Xander said curtly.

Spike paused, then said. "Getting. My. Soul. Back. Wanker."

A lot of the anger and power left Xander and he looked closely at Spike. Then he said, "How?"

"Ever heard of the Demon Trials?"

Xander shook his head, now honestly curious.

"They're a series of challenges, of tests that if a demon passes them, they can get a prize, a wish that would normally be impossible," Spike said.

"Then why isn't the world ruled by demons and there are still Slayers?" Xander said, eyes glinting dangerously.

"No demon's ever survived them, not in 10,000 years." He shrugged. "If I succeed, I… well, end up hopefully not too much like the poof. If I fail, you don't have to bother killing me."

Spike then yelped as a sharp telepathic probe sifted through his thoughts, then abruptly retreated. Xander nodded to him, stepping to the side of the road and said harshly, "If I ever see you in Sunnydale or near Buffy without a soul again, I'll end you."

Spike nodded jerkily and got on his motorbike, starting the engine and racing away. Xander watched for a moment, then disappeared. He flew north and west, crossing the Atlantic in moments, then shifting planes as he hit the Cardiff Rift. One thing he had discovered in the Time War was that Rifts in time were an easy form of transportation, particularly between worlds. And he was looking for a very particular world.

"BOB! DON'T LET THEM WIN!" Norman Osborn screamed, and everyone looked on in horror as the Sentry flew towards Asgard with the intention of destroying it. Before he could hit it, however, a white blur hit him hard and knocked him out of the sky. The second blur was hovering, apparently watching the no doubt surprised Sentry. Only Thor had ever been able to smack him around like that, and now even the Mighty Thor was having trouble. Everyone was gobsmacked. Even Osborn had shut up.

"Odin's eye," Thor breathed, feeling the dimensional disturbance. Then, incredibly, he smiled and said to himself, "It seems we have some assistance this day."

Xander dropped down towards the Sentry. He was wearing a similar suit to the Golden Guardian of Good, but he had altered it. Now it was white, with a golden cape and a golden W in place of an S. Thor followed him and nodded his thanks to the dark haired mortal, who nodded back.

"Thor Odinson. That isn't the Sentry," Xander said. "It's the Void, in full control."

Thor sighed. "I suspected it was so. Robert was always a little weak willed. And who are you, traveller?"

"I go by the Watchman, Thor," Xander said, then flashed a smile, and said, "but you can call me Xander."

By this time, the Void was watching them silently, doing nothing. Then it said, "So. One from beyond interferes. Well, we can't be having that." As it said that, it blasted Xander. Or tried to, as he negligently blocked and dispersed the blast. In response, the Void blurred, attacking Xander head on, and the two incredibly powerful beings began to brawl. Thor watched and waited for an opportunity to smite the Void, but it did not come.

Meanwhile, in Washington, the President was puzzled.

"So, the Sentry, who you say has power that's off the charts is being taken down by someone we don't even know about?"

"That's the basic idea, sir, but I wouldn't rule out the Sentry, or whatever he's become just yet." As he said that, the unidentified meddler was punched several miles away. This didn't seem to faze him all that much, and he just got up and took the fight back to the abomination that had once been the Golden Guardian of Good, landing a blow that smashed the Sentry into the water table.

"And what do we do now?"

"I think we should wait, sir. This new person and Thor seem to have the situation in hand."

Indeed, as the general said that, Thor whopped the grounded Void with an enormous thunderbolt in conjunction with a similarly sized blast of golden energy from the newcomer.

"So the plan is just to wait and see?"

"Mr President, we know for a fact that Thor or the Sentry could tear the planet in half if they so wished, and I have no doubt that this newcomer would have no problem doing the same. Not only that, but the Avengers are there. What could we possibly do that could make a difference?"