In an upcoming game I plan on the players eventually travelling the Webway chasing daemons & the BBEG. They will end up fighting their way through the Webway to the doors of the Golden Throne, bust their way in & then kill the Emperor of Mankind. Yep, I know it is hugely out off the box & one of those thing that you aren't supposed to change. It's against the spirit of the game. But from what I've read in the lore I think it would be an interesting story arc It doesn't end with him dead. He is reborn in the Warp. But in the intern the Astranomicon gutters & dies, huge warp storms burn with his fury & humanity is pushed to the brink. Right now I just need to figure out the best way for him yo be reborn. Should it be as Ynnead in the core of the Eldars Infitity Circut? As the Starborn, who us only born with the deaths of the Emperor's anti-warp children? Or something else? What are your guys' opinions on how I should handle it?

Thank you all for your opinions. I'm going to talk with the player & fluff it as the rat was psychically fused with warp energies to have almost human intelligence. When it died it was more individual than a normal animal & so loyal that it found a way to return to serve its master. (which was basically their idea in the first place) yes they will be a psyker idk if they want to actually look like a rat though.

I'm planning on running a Dark Heresy game & a player of mine had an interesting character idea. They want to play the reincarnated soul a rat which was the familiar of one of the shaman who reincarnated into the Emperor of Mankind, I really like the idea but I'm not sure how to represent it in the game, can rat souls become human souls? Would they maybe need some rat DNA in their genes? How would a rat-genespliced human be represented?