Lord Kaldor Draigo, Supreme Grand Master of The Grey Knights
Being both famed and cursed upon his first dealing with the daemon prince M'kar The Reborn, Draigo was yanked into the warp by the out-phasing M'kar on their second meeting. For untold time he has wandered the Realms of Chaos slaying daemons and traitors alike. No foe has ever had the best of him, and now only the most crazed Khornate followers will knowingly oppose him. But in the impossible Realms of Chaos, Draigo is himself an impossiblity. He can never restore order, and every time his zeal has destroyed legions of daemonic followers, they will always return.
Recently he has experienced being drawn from the warp as any other daemonic creature, through the sorceries of corrupted psykers, and several times has he been reunited with The Grey Knights. Fighting alongside his brethren untill his eventual departure back into the warp like the daemons they slay.
Errmmm...what? The highlighted bits stand out the most "Wait..what?!" worthy of all of that. Two queries:
1. How can a material being such as a human (albeit, Astartes) withstand being in the warp? The warp has no natural dimensions, the laws of physics mean nothing. Force? Worthless. Atoms? Playthings. Cellular structures? Ha, get real. The only reason ships aren't torn apart by the sheer random chaos of it all is because of their Gellar fields, and even these can buckle under the supreme strain of the crashing tides of the warp. How does one lonely Astartes not get torn to pieces in seconds?
2. He can be summoned! Even if he could have survived in the warp, how does he get accidentally summoned by corrupt sorceries? From what you read in the Chaos Daemons codex, it would appear that when a warp rift is being opened for daemons to pour through, the daemons congregate on the other side, waiting to be loosed on the material universe.
I can't really imagine Draigo standing shoulder to shoulder with a bloodcrusher listening to how it's Khorne's "Time of the millennia", exchanging psychic tips with a herald of Tzeentch and gossiping with a seeker about who is Slaanesh's latest sex-toy.
If nothing else, I'm not seeing that part, if any, of Lord Kaldor Draigo (if that is his real name) being legit.