The Archdemon VS The Mad Titan

After blasting Diablo away, Thanos looked at the soul stone on his gauntlet. Just one of the stones and he felt stronger than ever. However, he knew that if he stuck around the one who had the other five would take the chance to murder him.

"Prepare to leave."

Thanos was going to use his magics to teleport to the other side of the universe as just one Infinity Stone was a relic of nearly limitless power. Five of them would grant one power beyond imagination, but just as he prepared to cast his magic all of Vormir was enveloped in a potent barrier. 

Thanos' spell was instantly destroyed causing him to frown. He had made sure to infuse the Soul Stone's power into his magic, but even then it got canceled. At that moment, he felt what he could only call the Soul Stone's fear.

He looked up into the sky where he saw Samuel less than 30 meters above him. Thanos just knew that he had no chance of defeating that monster as his presence caused the Soul Stone to transmit its pure fear to him. 

Samuel also wasn't alone as he was surrounded by creatures and beings with destructive power. Giratina, Dialga, Palkia, Puck, and Mag'aladroth. Thanos had ignored 2B and Grayfia even though that was a bad idea.

Samuel was the first to speak which snapped Thanos and his children to focus. 

"Thanos of Titan, you have something that belongs to me and I have no intention of leaving without it." 

Thanos didn't fall to despair instead he raised his dual blade at Samuel. 

"No matter how powerful you are, my mission takes precedence. I won't just give up the Stone to you."

Puck who was flying above Samuel's shoulder snorted. He started to shadowbox and smirked at Thanos. 

"Tough words raisin. Come on boss, let me at him." 

As Puck said that his form started shifting as he began to revert to his true form. With Samuel's boundless mana reserves, Puck could use his world-ending powers without end. Before Puck could finish, Diablo appeared next to Samuel completely unharmed. 

He grabbed Puck by his nape with a terrifying smile. 

"Puck, are you trying to take my opponent?" 

Puck began to swear as he reverted to his cute cat-like form. 

"Of course not, I was just going to warm him up for you." 

Diablo smirked as he handed Puck back to Samuel. 

"Leave to me, my Lord. I gave you an oath and I do not break my word." 

Samuel smirked. 

"I will hold you to that Diablo." 

With a smirk, Diablo flew forward before Samuel and his entire group flew back giving him space. Diablo turned back toward Thanos and his surviving Black Order. 

"That last hit was quite powerful. Though, only quite." 

Diablo spread his arms out before his magic began to flow out of him. When Samuel had created Diablo, he couldn't have created the most powerful form of Diablo. As such, he created him with as much energy as he could spare. 

Regardless, Diablo was still one of Samuel's strongest servants aside from his gods. Ebony Man, Cull Obsidian, and Corvus Glaive began to step forward as they were going to aid their Father. 

However, Thanos had a better use for them. 

"I am sorry for this, my children." 

He raised his left hand and using the Soul Stone which amplified his magics he pulled their souls right out of their body. The three didn't even have a chance to react as their souls were torn apart and devoured by Thanos to increase his power. 

He was already an Eternal with Deviant genes blessed with power from birth, but he increased his power once more. Normally, devouring souls was risky, but with the Soul Stone, the risk was mitigated. 

Diablo nodded as he sensed Thanos' magic and cosmic energy increase. 

"That was the correct thing to do, they would have held you back. Now then, let's begin." 

Diablo without missing a second, waved his hand burning 10 lances of black burning fire. With a snap of his fingers, the lances struck Thanos before they detonated in 10 gigantic black mushroom clouds. 

"Nuclear Magic, quite explosive wouldn't you say?" 

The mushroom clouds suddenly exploded outward as a massive blast of cosmic energy was fired toward Diablo. Diablo waved his hand as a wave of dark purple energy slammed against Thanos' attack. 

Everything around Diablo began to turn to dust which canceled out Thanos' attack. Samuel saw that Thanos was unharmed as he had raised a barrier when Diablo's attack hit. 

Thanos stepped out of the burning crater he was in as he looked up at Diablo. 

"Quite a lot of power for a mere Butler." 

Diablo just smiled with pride. 

"My Master is the most powerful being I have ever met. It was his power that gave me life and by killing you, I will be granted even more strength. Until then, entertain him with your resistance." 

Diablo suddenly disappeared which caused Thanos to spin around with his sword. Standing directly behind him was Diablo who extended the nails on his right hand into black claws. 

With these claws, he began to clash against Thanos' sword which could even cut Vibranium. Thanos began to draw more power from the Soul Stone which flowed into his soul. This energy flowed into his body making him faster, stronger, and more resilient. 

The magical and cosmic energy in his body began overflowing causing the Mad Titan to become a truly terrifying opponent to anyone else. Suddenly, a dense demonic aura burst out from Diablo as he got faster and stronger. 

Thanos swung his sword causing a massive slash to tear toward Diablo, but the Demon merely spun around before slashing Thanos' left leg open. Thanos didn't react to the pain as his own natural regeneration made wounds like this obsolete. 

However, he noticed that his wound wasn't healing as fast as it should. He didn't get to think of this as Diablo slammed his leg onto the ground causing everything for thousands of meters to burst into bright blue fire. 

Thanos protected himself by forming a barrier from the Soul Stone's energy. However, Diablo merely used the fire as a distraction. He got into Thanos' guard before he slashed the Titan's barrier open along with his stomach with his claws. 

Diablo stepped back as Thanos' gut burst open causing his intestines to spill out. Thanos however reached down and grabbed his own guts before he began to push them back into his own stomach. 

Diablo watched on with fascination as the wound began to close rapidly. In the main universe, Thanos had survived being reduced to a skeleton before regenerating. Even this Thanos possessed a potent Eternal regeneration factor. 

Once the seemingly fatal wound healed Thanos picked himself up off the ground. 

"That hurt." 

Diablo's claws retracted as he reached up and cupped his chin. 

"So gutting you and cutting you isn't considered a fatal wound? Here I thought that wound would have finished you off. Guess I can push you a little harder." 

When Thanos heard that, he looked back toward Samuel who had sat down on one of the surviving mountain peaks. He was just relaxing on a chair while the silver-haired maid served him some drinks. 

Thanos grit his teeth as he isn't even facing the Master, just his butler. Then again, he wasn't just going to be entertainment." 

Thanos spun around before he raised the Soul Stone toward Samuel. From the Soul Stone, a blinding orange blast surged toward Samuel. Diablo didn't interfere with the blast, but he was definitely not happy. 

Moving many times faster than before Diablo appeared in front of Thanos. He stabbed his claws directly into the Mad Titan's guts, but he didn't cut him open. Instead, he used his Nuclear Strike magic directly causing the equivalent of a nuke to go off inside Thanos' body. 

Black flames began to burst out of Thanos' mouth, eyes, ears, nose, and every other orifice in his body. Diablo pulled his claws out before he stabbed back watching as every piece of flesh on Thanos' skeleton was vaporized. 

As for Samuel, when the blast reached Samuel without even looking he used his amplified time magic to freeze it in place, once the attack was frozen he put down his tea cup before he began to absorb the entire blast into his mouth. 

In a few moments, every last speck of energy was swallowed by him. 

"Not bad." 

Grayfia smiled as she refilled his tea cup. 

"Would you like anything else?" 

"Some good tacos wouldn't be a problem." 

As if prepared, Grayfia waved her hand causing a large plate full of Mexican-style tacos to appear before him. The meat was actually Triceratops meat from the former Savage Lands. Alongside, it was some cilantro, lime, and some Mexican sause. 

"Thanks, Grayfia." 

Without even looking at the fight he just began to enjoy Grayfia's cooking. Puck landed on the small table before he picked up one of the tacos. 

"Yummy." 

Meanwhile, Diablo glanced at the bare skeleton of Thanos which was still standing. 

"Oh my, I thought that would kill you." 

Sword in hand the skeleton swung his sword at Diablo who deflected the blade. Diablo watched as flesh began to flow over the skeleton rather quickly. It started with the head before the flesh began to return piece by piece. 

Diablo was very amused at this so he waited until Thanos had fully healed. Thanos clenched his fist as he drew on more of the Soul Stone's power. 

"I WON'T BE MADE A FOOL!" 

Thanos lunged at Diablo, but the Demon stabbed his entire hand into the chest of Thanos. In the same movement as Doctor Doom, Diablo tore out Thanos' entire spinal cord and skull. 

Thanos' body began to twitch as it still held his sword. Diablo thought that was it, but Thanos' body clenched its fist once more. The soul of Thanos despite its death stayed in its body before it used its full concentration to infuse his sword with the Soul Stone's great power. 

In a devastating move, Thanos swung his sword unleashing a soul-rending attack at the Demon. Right after the headless and spineless body fell down dead. As for Diablo, he raised a powerful barrier that stopped Thanos' final attack dead in its tracks. 

Diablo was going to claim Thanos' soul as Samuel had said he wanted the soul of the Titan. However, Diablo couldn't find it which made him look at the Soul Stone. 

"So he used his own soul as fuel for that final attack. I failed my Lord." 

Diablo reached down and picked up the Soul Stone which trembled in his grasp. Using simple magic he caused the body of Thanos to float behind him. He then teleported to Samuel who was still eating his tacos. 

When Diablo arrived he dropped the skull and body of Thanos before he kneeled before Samuel. 

"I must apologize, my Lord, I failed in my second task. Thanos used his own soul as fuel and I couldn't claim it. I can only offer this in return." 

Diablo raised the Soul Stone toward Samuel who reached down and picked it up. 

"You most certainly didn't fail." 

Already he could feel the energy of the Soul Stone reacting to the other five in his heart. He placed his hand over his chest before he directly pulled out the Mind Stone from his World Sage heart. 

The stone was ejected from his body by his viral matter into his open hand. 

"Time to begin my plan." 

Samuel closed his eyes as the Mind and Soul Stone began to spin around. He pulled the Soul Stone directly into his soul while he placed the Mind Stone inside his head. He no longer had a brain as his entire body was Viral Matter. 

However, he began to turn the Mind Stone into an artificial brain in his head. As for the Soul Stone, once it was inside his soul it resonated with Power, Time, Space, Reality, and the Mind Stone causing all that energy to flow into Samuel's body. 

Samuel stood up from his seat before he spread his arms out. His already extreme levels of strength rose a level, but it was going to be even stronger when he finished creating his next set of beasts. 

"First, it's time to awaken my Soul Beast." 

Samuel began to surge the combined power of the 6 Infinity Stones, his potent magic, the Divine and Infernal Power he had inherited from Arimane along with some of his own Life Force into Annihilation Maker. 

In particular, it was the reforming consciousness of Tiamat which began to form a powerful soul. A Soul Beast would be the other half of their summoner, their fates would be bound together and they would grow stronger together. 

Through this process, the soul of Tiamat was removed from Annihilation Maker as the Sacred Gear's powers were crucial to Samuel. After the separation was complete, the Soul of Tiamat devoured half of his mana, Divine and Infernal Energy in one go. 

His reserves would recover, but not just that plenty of Soul Energy from the Soul Stone was used to stabilize her reborn soul. Once the process was complete the soul quickly left Samuel's body before it began to take shape.

The soul quickly formed a body which he recognized as he had shaped her himself. Tiamat is a woman with long light blue hair and large curved horns, but much smaller than the original. In terms of height, she was shorter than Samuel at 5'10, but still, she was beyond beautiful. 

When her eyes opened they were bright crimson with large X-like symbols in them. Samuel was going to say something, but Tiamat didn't give the chance. She wrapped her arms around him with a hug. She had a small smile on her face, but when she looked up at him he saw pure love in her eyes. 

"Darling, my partner." 

He had not expected that reaction, but maybe it wasn't so bad.

(Image here.)