From what I remember, his name was: MissingNO (I think) and here's a message from my best friend where he talks about him and tells the lore of his OC (please don't criticize me, criticize my friend, he made the OC)
"Hello!! I hope you don't come at me with torches. I've created a Pokémon story (a rather dark and mature one) that's different from all the others. Why? This story will be called Pokémon: Consequences. Imagine this: we all know that Giratina is king of the Distortion World, but what if it isn't? What if it's simply a jailer? Well, in this story, it will be revealed that our beloved ghost dragon is nothing more than a jailer of something more "evil" that dwells there. That something is called MissingNO., who has stabilized its glitch and now wants revenge on its own father, Arceus. This story will unfold across four narratives (Paradise, Postmortem, Ragnarok, and Last Day), in addition to a video game called Rotten Shadows. In this game, a glitch traps Arceus in a dimension he created (Arceus is transformed into a person by MissingNO.). To make him suffer, he will give him many tasks to complete to see if he deserves to live (yes, it will be a survival horror game). The player must survive MissingNO.'s games while being relentlessly hunted. The game will feature new mechanics: Unreal Engine 5, highly developed hearing, extremely intelligent AI, and something called crests (depending on which crest MissingNO uses, the mechanics will change; one turns off the light, another forces you to stare, and another randomly changes location). It will be completely free for all platforms (except mobile). I don't have a release date for either Consequences or Rotten Shadows yet, but I will do everything possible to release it as soon as possible."
by Matiasprox3000