Out of the 4 ruinous powers, one could say Tzeentch is the scariest to be possessed by.
Khorne's possession is like giving in to the red mist and venting out your rage for eternity.
Slaanesh's possession is like a high with bouts of clarity before falling into another high until all you can do a seek an even greater height.
Nurgle is like being overcome by anxiety and depression until you forget it and continue on as a husk.
But Tzeentch is different because you don't even know it until your usefulness is up. Using your own arrogance against you, you believe your actions are of your own accord. Even if you find out, you believe it's only for a moment as all are a part of his great plan. In the end, it's only once you are no longer of use that you know you were a mere toy to the outer God of change/hope.
In the maze of perpetual change, a familiar figure walked around perfectly, navigating the realm of Tzeentch. His appearance changed, and he looked exactly like Odin except for minor differences. His hair was White and reached down to his hip. His eyes were heterochromatic, having scarlet red and grey eyes.
Playing with strands of his perfect hair, the guardian looked around and took control of the realm, bending it to his desired will. To the guardian, this entire universe was nothing but a mere game, actually, that was too high of an appraisal. This world was more like that boring idle game you would play when you had nothing else to do.
Tzeentch was nothing to the guardian. He had met stronger literal ants than Tzeentch one had even eaten a quarter of reality, which held around 72^100^100^100^100^1,000multiverses. He made his way towards the weaver of fate and made his introduction to the terrified Chaos God.
"Hello, Chen. I am the one. It is a pleasure to meet you." the guardian said, as did a courteous bow.
The guardian looked at the true form of Tzeentch, and he smiled. His smile seemed to distort as he said the next few words.
"I should reveal my true self. It would be rude as I can see you but you can't see me." the guardian's form changed and incomprehensible images soon covered the warp.
Tzeentch could pride himself on his knowledge, his plots, or his secrecy, but compared to something like an outer God, especially the one that made them, Tzeentch understood what it was like to be one of his pawns.
Everything he saw existed and didn't whispers and screams that seemed to tear his essence assaulted his mind. His identity was reformed to the outer God's image, broken and left insane for what seemed to be trillions of years before he returned, and everything seemed normal.
The repaired Tzeentch felt like it was a nightmare, but one word controlled it was real.
"Ky" (pronounced Kai)
The Guardian wandered around the galaxy after his prank and watched the boring life of the galaxy. The only fun thing was the Tyranid hive mind, which came from the Alico galaxy, which the guardian was familiar with. The hive mind and the guardian had quickly become friends in mere minutes after talking about stuff.
He had also made friends with some watchers in the dark and talked about things outside the universe. He had also talked with the star child. As the guardian was, Odin he had the same ability to make friends no matter what.
The guardian wondered why the real Odin had chosen this universe. Sure, it might be a challenge to mentally challenged people, but for Odin? If Odin wanted, he could use soul magic and fix this with a snap. Even right now, the young Odin could do it if he was taught how to.
It was one of the reasons he was feared, no matter what, he had an unbreakable will that was beyond fate and could influence it whenever he wanted; he had an infinite soul so he could use soul magic and destroy reality whenever and recreate it, and he was true chaos, never on one side but omnipresent on both at the same time.
The guardian was truly wondering what Odin was thinking but in the end, even Odin couldn't tell what another Odin was thinking, so why bother just let it play out and enjoy the show.
"Also, now that I think about it, how is the kid going to deal with the racism in this galaxy? I hope he doesn't have his feelings hurt?" the guardian muttered as he played around Sagittarius A star.
"Who are you talking about?" the star child asked.
"Oh, about my other self or realm me, I'm just a shard of his soul." the guardian replied.
"I see."
"Hey little one, do you want me to restore you to what you once were?" the guardian asked.
The star child widened his eyes as the guardian held the rest of his soul and consciousness.
"Actually, never mind forget I asked." the guardian said as he disappeared appearing in a new part of the galaxy.
He appeared in the hall of victories in an area of the Sanctum Imperialis. The Guardian smiled as he looked at the many creations of man some he had taken part in, but he also studied the items the humans from 40k had made. Such as a part of the first warp drive, a Gellar field, and the Mendelian Eukaryotic Genesis Formula, which allowed for the first cloned human.
The guardian completed his tour and left for the other areas of the palace. Heading for the Hall of leng he was undetected even if he walked in plain sight. The hall of leng was a residence of the emperor where he used to measure the angles of space and time. The Hall exists on a pulled thread in the fabric of space-time, giving the space a chronological distortion.
Entering the hall, he could see temporal distortions. It was well interesting but had nothing cool, so the guardian left and went to the rest of the places in the palace. He soon toured the entire area and headed for the dungeon. The dungeon had a much more different mood. The top held a more regal, arrogant display, but the dungeon held a sorrowful display.
The walls seemed to mourn their owner. He felt as the surrounding radiation increased as he came closer to the throne room. The defense got tighter and tighter from custodians roaming in eternal watch to sisters hiding and roaming in the dark.
As he walked by, he thought if he should take a custodian and a sister of silence and use them as a reward for Odin. But he thought of what should merit this reward should he give one when he conquered a world or something else?
'They say a custodian armor and weapons are worth in not gold but worlds, so I guess I should have the kid conquer an entire system before giving a custodian, but then what about the sister?' the guardian thought.
The sisters of silence are blanks people who have no connection to the warp their ability is a direct counter to psykers as they can weaken or fully nullify a psykers powers. To demons and other beings of the warp, humans are like candles in the dark they shine, but they're dim psykers and Eldar is like a bonfire but blanks are like an abyss.
Blanks are also incorruptible, so the forces of chaos can not possess them. They can also interfere with the Tyranid hive mind connection. Blanks released an anti psyker aura, which makes any being feel a sense of wrongness and for more powerful psychic beings, it can hurt or even kill them.
Because of this aura, many blanks do not live long as most have an unknown ill intent for them. They have many foes and few friends. The gene that gives birth to blanks is also rare that only one person in a world might have the mutation in a generation.
'Well, they're anathema to chaos so I guess if the kid kills a greater daemon or demon prince of Tzeentch ill give him the barbie doll for his experiments.' the guardian said as he snapped his fingers and two people disappeared that day two people that were forgotten by existence.