Destruction of the many buildings around the area was all that the now weakened All Might could see, all but All for One from the League of Villains were now long gone, but what he was more focused on now was what he was just told. Shigaraki was apparently his now deceased master, Nana's grandson. The shock of the revelation had shaken him to the core. All for One was probably smirking with glee under that metal mask of his. He couldn't find the strength to stand up to the tyrant before him, until he heard a single voice.

"Get up… All Might… please… we need you!" came the voice of a young lady that he just recently defended, and that wasn't all. Despite not being anywhere near him, he could faintly hear a crowd of civilians cheering him on, including his pupil, Izuku Midoriya. Like magic, he activated One for All in his right arm.

"Fear not miss," came the number 1 hero's reply. "You're right! A hero has so much to protect in this world! Which is why I will defeat you!"

"Let's skip the facts on heroism and focus on reality," All for One coldly spoke. His right arm began to expand into an amalgamation of different quirks. "Springlike limbs… kinetic booster x4… strength enhancer x3… multiplier… hypertrophy… rivets… air lock… spearlike boots… the shockwaves until now were just to weaken you out. In order to kill you, I'll punch you with the ultimate combination of quirks I have within me!" All Might draws his buffed arm back, ready to counter the soon incoming attack from his greatest adversary. "One for All no longer dwells within you… all that's left are nothing more but mere embers of a raging inferno that you've already passed on, and they get weaker every time you use it. Now it's just a feeble spark about to put itself out." The villain then flew at All Might using one of the quirks he stole… "Izuku Midoriya!" ...and caught All Might off guard upon saying the successor's name. "He's the one you passed One for All onto, isn't he? I bet he came here without your consolation! He's reckless… which means you'll die full of regrets All Might! As a hero, and as a teacher!"

The two powerful beings finally clash their fists. The shockwave generated from it was so powerful it caused the air around them to warp. Just as it seemed the two were evenly matched, All for One called on the power of another quirk. "RECOIL!" As the name suggests all the power of the punch All Might threw was then recoiled back into his own arm, blood spewing out like geysers from the damage dealt to him. This also caused him to falter in his stance, being pushed back and seemingly knocking him over…

"If you feel like you cannot go on, remember…" came the voice of his old master within his memory. As he was about to hit the ground, he planted his left leg behind him and transferred One for All into it as well.

"I'll beat you, not because I'm a symbol, but because I will do exactly what my master once did for me… until I finish training young Midoriya… I won't..."

All for One simply looked at the weak hero in boredom. "It's embarrassing how resistant you are…"

"...I refuse… to die!" Instantly All Might's left arm was buffed as his right arm was weakened back to its original state, allowing All for One's arm to pass by him as he used it as bait while swinging his left arm for a strong left hook to the villain's head, breaking his mask.

The villain smirked at his opponent. "A clever trick, how unlike you…" and his grin then turned more sadistic. "...but with a weak punch like that, you don't think we would be defeated so easily?"

Just as All Might was about to transfer what was left of One for All into his right arm for a final blow, that last sentence caught him off guard. "We?"

"Yes…" All for One said as purple biomass rapidly covered his body, except for his amalgamated arm, and the familiar face of white evil eyes and sharp teeth in a wicked smile could be seen, but instead of a kind hearted feeling one would get upon looking at Deku's face, this once was filled with nothing but sadistic malice. "We…"

Before All Might could blink, the villain's coated left arm, punched the hero in the abdomen, sending him flying into the debris behind him, where he laid barely conscious. "It was pathetic really, to think that you could defeat us. Over the years you have gotten weaker All Might, but upon us bonding, we've become even stronger then when we last battled. You never stood a chance against us." They then gave an evil, erie laugh that sent chills down the spines of anyone who heard it. "Once we finish you off, we will claim this world as our own, and after that, we will conquer the next planet, and the next one after that! We will raise hell to the whole universe until it is beneath our foot, for we are Diablo, the God of the Klyntar, and eventually the God of everything!"

All Might could barely hear anything Diablo had said due to the constant ringing in his ears, but from what he did hear, it wasn't something he liked the sound of. "Becoming a god… is he serious?" he thought.

The bonded monster slowly walked toward the fallen hero. "It has been fun All Might, really it has, but we're afraid that this little game of hero vs. villain must come to an end…" they then raised their amalgamated fist up for one last punch, only for a dog covered in a familiar orange symbiote to bite onto Diablo's left arm.

After shaking the mutt off, the symbiote god looked on in anger at the orange one's betrayal. "Cross… What are you doing here? Aren't you supposed to be bonded to Katsuki Bakugo?"

The dog only growled before it spoke. "What I did, I did for the good of the klyntar race, but it turns out that for all these years you lied to us. We all thought that by taking over these planets we would be able to preserve our race from dying, but no, it was all a ploy so you can become ruler of the universe…"

The purple devil only smirked at Cross' analysis. "My, how perceptive of you."

"You lied to us! We never needed to conquer worlds to preserve our race, and that klyntar, the one you banished was proof of that!" Diablo's eyes then locked onto Cross, his attention fully on them. "We fought them well, but their bond with their host beat us in the end! I will face you here and now, in order to make sure their ideals come to fruition!"

Diablo just stared at the symbiote dog for a second, before then laughing their ass off. "You think you could defeat us?! We are your god! We can just take control of your mind with a simple thought, but we will humor you! Face us if you dare weakling!"

"With pleasure!" Cross then charged at the terrifying monster before them. Using the claws on their paws, they made quick slashes at the symbiote, but the wounds healed as soon as they were formed, and it looked like they weren't in any pain whatsoever. Before long, the dog was grabbed mid-slash, and pulled to Diablo's face.

"Was that all? How disappointing," they said as their jaw unhinged. Knowing what was coming, Cross uncoated from the dog's head and disconnected their link to the dog's brain before Diablo chomped down on the poor mutt's face. A sickening crunch was made as the dog's life was instantly ended. The body was then thrown to All Might who had miraculously managed to stand despite the possible concussion he received, but even so, he couldn't find himself to fight. He watched the battle between the two and saw no way of beating this monster. This wasn't just some uphill battle, this was a clifface, a straight shot up, maybe even slanted upwards to make it even more impossible than it already is, maybe in his prime, he would've had a chance, but he's not anymore. All he has left is a lingering ghost of his power. All that was left was enough power for one strong final attack, but he doubts that he'll get a chance to use it. He wasn't even sure it would work.

"So…" Diablo began. "Are you going to fight, or have we finally outmatched you All Might?" There was no response, and that sent greater fear through everyone currently there. "We thought nought… Suppose you won't keep your promise then."

In a single bound, Diablo cleared the distance between the two, the amalgamated fist drawn back, and then swung…

…

…

…

…

…

…

…

…

...but it missed.

At the last second, a tendril from Cross grabbed All Might's back and pulled him out of the way of the overpowered attack.

"W-What?"

"Hey, hero…" came Cross' voice. "You're supposed to beat the villain, not let them kill you."

"...But how?" He didn't want to say it, but it's the truth, how could he beat Diablo? He barely managed to win the first time they fought, and then they say that they were far more powerful than what All for One was at that point, and they certainly had the power to prove it. "How do we beat him?"

"That is the question, but I think I might have an answer to it," Cross said. "We both can't take him on by ourselves, but together… maybe."

All Might then looked at the symbiote in shock. "Are you suggesting we..?"

"I don't have any better ideas, you got any?"

"Of course not," the number 1 hero said. He then contemplated the symbiote's offer, but seeing Diablo rise from the wreckage they caused due to missing All Might was all he needed. "Looks like we have no choice…" He then held out his left arm, to which the symbiote climbed up and coated his arms, body and legs, healing any damage that was taken and increasing their current strength.

Diablo noticing the team up before him only smiled cockily. "You think bonding with each other will give you a chance of victory? You can't possibly hope to defeat us!"

"I'll focus on keeping your strength increased and healing your wounds," came Cross' voice in All Might's head. "You focus on the battle tactics and such."

Diablo then attacked again, only to miss as All Might dodged the giant fist with speed that was in parallel to that of his prime, and All Might noticed this greatly. Flexing his arms, the coated appendages buffed up to their usual size and attacked. The force of the punch was also on par with that of his prime, and he wasn't even using One for All! He continued in this attack pattern of quick strong punches and quickly dodging Diablo's counter attack. One disadvantage to having such a big arm was that it slowed his movements.

After taking a lot of attacks, Diablo then mockingly laughed as All Might stopped before him. "Despite your bond bringing your power back to your prime, those attacks are nothing but weak punches to me!"

Despite what they said, the hero did not falter as he drew his fist back, his left arm being uncoated of the mass as it moved over to reinforce the right arm, Cross having predicted what All Might was about to do. "That's because, I DIDN'T PUT MY BACK INTO IT THAT TIME!"

With all the remaining power he had left, All Might charged the last of One for All into his right arm. Sensing the amount of power emitting off of the arm, Diablo seemed to sweat a little, but that sweat became a slight panic as they say bits and pieces of Cross were being torn to shreds and disintegrated due to the power of One For All. In a last ditch attempt to stop him, they charged their left arm up for a shockwave and released it, only for All Might to quickly dodge the blast thrown at him by using his regained speed to close the distance between them. With great determination, he called more power into his arm, making it glow a bright orange as he swung, landing the punch right into the monstrosity's face.

"Goodbye, All for One!" All Might exclaimed.

"And goodbye Diablo!" Cross added.

"UNITED STATES OF SMASH!"

The best way to describe the power from the attack was like that of a small nuke. In the fallout of the attack, the energy emitted from One for All caused the symbiotes' biomasses to disintegrate almost instantly.

"Heh, I guess I'll never find that perfect host that Deku was referring to." Those were the last thoughts of Cross before One for All's power ended their existence.

When the dust finally settled, a crater was seen, at least 100 feet in diameter, and in the center of it all, was an unconscious All for One and All Might standing above the villain, but Diablo was nowhere to be seen.

"He… He won… ALL MIGHT WINS!" came the voice of a reporter riding a helicopter. Cheers were heard and all the bystanding heroes present ran to the center of the crater, but upon seeing the two combatants closer than 50 feet away, they saw a shocking sight. All Might was alive, but his right arm from the elbow down was gone, as though it had been blown off by a hand grenade.

Soon government officials came to take All for One to the high security prison, Tartarus. As news reporters flocked to the scene, All Might deciding to make one last declaration, using his left arm, he pointed at the camera and said, "Next, it's your turn."

Only one green haired kid in the crowd and his symbiote friend knew what that message meant, and they cried for it. He was done, he had no more power, One for All had finally left him.

"Oh how sad…"

Every camera in the area turned their attention to the voice's origin, and there, laying on the ground, was half the familiar face of Diablo. Despite still managing to survive the attack, the last of their life was fading from them, and they decided to say their last few words. Words that may bring the world into an age of chaos and ruin.

"…Know this humans, I am not the only one of my kind on this planet. My legacy will continue where I left off, assemble an army, and conquer your… pathetic… planet…"

And like that, Diablo, God of the Symbiotes was dead.

In an old abandoned warehouse, Shigaraki was staring off into the vast openness of the new city before him, reflecting on what had recently happened.

It was right after Bakugo had been saved by Izuku, Deku, Kirishima and Todoroki. Soon after that, more pro heroes showed up. They were easily overwhelmed. Seeing one of the only ways to save his successor, All for One forcefully activated Kurogiri's quirk to open a warp gate to the warehouse they were in now, and after activating Magna's quirk pulled everyone into the warp gate, but before he was pulled in, All for One grabbed Shigaraki and put his hand on the teen's chest, and felt something enter his body. Before the villain let go, he said only three words.

"Protect our legacy."

After awhile, Shigaraki finally figured out what it was that he was given, and it seems they finally wanted to talk.

"So… who are you?" Shigaraki asked the dark grey tendril with an evil face.

"I am Lucifer, God of the Klyntar, and you, are mine."

End of Phase 1

Author's Note: Wooooo! That was exhausting to finish… man writer's block sucks! Sorry I didn't update this story sooner, but I hope it was worth the wait! Anyways, Phase 1 is over. Sorry if this seems MCU-ish but I felt this was my way of saying, I'm done with this story for a while. It has been fun writing it, but I need a long break from this story. At this point, I've pretty much exhausted most of my ideas for it. I'm thinking of returning to my Yu-Gi-Oh! Vrains story or MHA/MLaaTR crossover. Until next time Excelsior! Plus Ultra!

New Update!: I decided that after all this time, this story has gone from being based off of BlackBlade567's story to becoming it's own, so from here on out 'We are Deku' has been changed to "Our Symbiote Academia".