Necrons are one of the oldest races in the Warhammer 40K universe. More than 60 million years ago, they waged war against Old ones and later allied with C'tans (Their Star Gods) to win the War in Heaven.
To achieve victory, Necrons (previously known as Necrontyr) traded their weak flesh for an immortal mechanical body with an unimaginable level of technology by going through Biotransference. Unfortunately, it cost Necrontyr their souls, which C'tans consumed and took command of their race once and for all.
By the end of the war, Old Ones were no more, and C'tans began to fight each other. Seeing once and only opportunity, Necron's leader, the Silent King, led a rebellion against their Star Gods and ultimately shattered C'tans into countless shards, scattering it all over the galaxy.
In the end, the Necron race went to Great Sleep to wait until the time was right and once again able to retake the Milky Way galaxy as they are destined to. With many worlds turned into tomb worlds, very few Necrons stay awake to watch over them and wait patiently as the galaxy continues to change and many races come and go while Necrons wait for their Silent King to return from his self-exile.
Trazyn the Infinite, on the other hand, took a different route during the 60 million years of his life. Unlike his Tomb World guardian colleagues, he dedicated himself to collecting and preserving the galaxy's history for Prismatic Galleries. This mainly involves stealing from other Necron Tomb Worlds, raiding the world before their extinction event, and trickery by any means possible, including waging decoy wars for decades. In short, Trazyn is a soulless robotic skeleton with Kleptomania with plenty of time to wait out the entire race just to steal a few artifacts.
Of course, Trazyn is a Necron Overlord, which means he has great authority, such as command of legions of Necron Warriors and rule of many Tomb Worlds. With his advanced robotic body and weapons from War in Heaven, Trazyn is considered one of the powerhouses of the Necron faction (Even though he doesn't prefer fighting as he wants to keep his enemy in pristine condition for eternity).
To catch and contain his collection, Trazyn uses mind-shackle scarabs to hold control of other alien races and command them like a puppet. This is how the Eversor ȧssassin was sent to kill William; Archbishop Elashor Herydark (His head is gone, but he did have scarab) was sent to form an alliance to retrieve the Duchess and King Benton's gifted ring that contained the smaller scarab variant to make diplomacy much easier.
His staff, Empathic Obliterator, is a unique staff, rumored to be old as War in Heaven and believe to contain the technology of the Old Ones. The staff has the power to kill an enemy and creature with a similar mind and purpose by generating a shockwave from Trazyn's body. In short, if Trazyn kills one Space Marine with his staff, he can kill an entire squad of Space Marines with a shockwave burst due to their similar mindset and purpose to kill Trazyn in the battle.
Finally, Trazyn has surrogate hosts in his arsenal. Because he made many enemies due to his occupation, he utilized an arcane device to take over his underling's body if he ended up dying or damaged. Once transferring his memory, consciousness, and war gears are complete, Trazyn can morph the new body into the identical body of his old one. This is why he earned himself a nickname of 'the Infinite' as he rose from thousands of death multiple times throughout eons.
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"It's a shame. I was going to retrieve that unique elder after I complete my mission to collect specimens of this world. The good thing is there is plenty of his kind once I finish my work here." Trazyn the Infinite said to himself aloud while his green energy shield blocked multiple bolter rounds, Heavy Flamer flames, and plasma shots from the plasma pistol coming from four Black Templars. With his plan ruined and the loss of many new collections, Trazyn decided to restart from scratch, starting with Emperor's Champion.
"I was going to capture you near the end ever since you slaughtered the Orks of this world. Who could have guessed that you were the one who killed my Ork raid bands from Greenhills and Ork kidnappers from yesterday? If you want the job done right, do it yourself. Let's start with you." At the end of the sentence, Necron Overlord opens the dimensional pocket and pulls out four Tesseract Labyrinths (Two cubes are empty), fist-sized cubes capable of capturing many living creatures against their will.
With a simple throw from the Trazyn, one empty cube went towards William as he continued to fire his heavy bolter. Just before the Tesseract Labyrinth cube could hit William, one of the Black Templar intercept and immediately disappear as green energy consumes the Black Templar after surrounding him.
"Damn, that was a special Tesseract Labyrinth for the rarest specimen. Good thing I have a spare one just in case." Just before Trazyn could throw another cube, two remaining Black Templars (One Tech Marine and one regular) charge ahead with chainswords in their hands after witnessing one of their brother's disappearance. The Dorn's fury rushed out from the two Black Templars as their rage consumed their mind of any strategies, and only the wrath of their Primarch emerged.
"Die, you abomination!" The Tech Marine was the first to attack as his chainsword strike hit the green energy shield. His two Mechadendrites (Robotic arms similar to Doctor Octopus from Spiderman) were equipped with a plasma pistol, and the bolter pistol continues to fire point-blank range.
Meanwhile, after moving to the Necron's blindside, the second Black Templar swung his chainsword with all of his might. Unfortunately, all of their efforts were for nothing, as their attacks didn't even break Trazyn's energy shield or show any sign of depleting.
Seeing this, William equipped himself with a jump pack and changed his weapon from Heavy Bolter to Thunder Hammer, capable of smiting powerful strikes by unleashing tremendous amounts of energy at once. With a single thrust from the jump pack, William leaped from the ground and reached his target, close enough to fight in close combat.
William's Thunder Hammer strike hits accurately as stored energy within the weapon unleashes at the moment it hits the energy shield. The force generated from the hammer created a shockwave and loud noise powerful enough to shatter every glass window of the throne room. But to William's disappointment, Trazyn's energy shield remained unshattered while his two battle brothers fell into their backs due to the energy shield redirecting the impact force of the Thunder Hammer to two Black Templars.
Meanwhile, just like two Space Marines, many people, including nobles, Legellan priests, and guards, fell unconscious after witnessing a terrifying fight between demigods. As for Prince Benton, the Duchess and the queen took cover behind one of the marble pillars to shield themselves, which saved them from deadly small debris. As for the king, he remained untouched as Trazyn's energy shield extended to him as he is one of the collections for the New World expedition in Prismatic Galleries.
'You gotta be kidding me. I knew Trazyn is powerful for Necron Overlord, but this is too much for just four Space Marines.' After he landed on his knee, William thought to himself, right in front of the Necron Overlord, who remained silent until he saw the damage within the throne room.
"No, no, no. I can't have this remarkable room full of unique history to be ruined by our little fight. Let us change our location." Trazyn's staff shined bright, blinding the remaining people who survived the energy impact, and William and Trazyn disappeared from the throne room and reappeared at the outside royal courtyard, wide enough to fit an army.
"Now, it is just you and me. Emperor's Champion, eternity awaits" Just as Trazyn threw his last empty Tesseract Labyrinth cube at William, who was still on his knee when a hail of Heavy bolter rounds hit the cube and destroyed it in midair.
"What? Who dares to defy me?" Trazyn the Infinite enrages as he no longer has an empty Tesseract Labyrinth cube to capture one of the rare Space Marine for his collection.
"We do! Fire at will!" A single man in commissar greatcoat and cap came from the gate, riding on top of the Chimera (Standard Armoured Personnel Carrier, APC) with Heavy Bolter mounted on the top hull shouted as William's main force, including the rest of the Black Templars, rushed in with weapons hot.
Commissar Ciaphas Cain, the hero of the imperium, honorary member of Valhallan Ice Warriors, and Tanna tea enthusiast entered the battlefield as he led a large number of various Imperial Guard. From Militarum Tempestus to Cadian Shock Troopers, all of William's forces open fire their weapons at Trazyn, bombarding and stressing Overlord's energy shield to its limit.
"Well, well, well. It looks like a vast number of potential specimens outnumbers me. But, this is why I brought my two additional Tesseract Labyrinth just in case." With that, Trazyn the Infinite placed one of the cubes on the ground and unleashed one of his collections at Astra Militarum.
Emerging from the pocket dimensional gateway, a large horde of savage warlike greenskins rush out with a battle cry loud enough to flinch Commissar Cain and veteran Imperial Guardsmen for a second. Leading the Warband, Orkboss armed with Power Klaw and Big Choppa unleash iconic warcry of the Ork.
"WAAAGH! Time to fight stupid humies, boyz!"