The Adeptus Astartes -- the Space Marines -- are the genetically modified super-soldiers of the Imperium of Mankind, sword to protect humankind from the great many things which threaten to destroy it in the grim darkness of the far future where this is only war, misery, and the ever-looming threat of extinction.

Sounds unpleasant, doesn't it? Well, there's one very lucky Space Marine, from the Space Wolves Chapter, who gets to escape all that and live in a world of adorable little horsies. How, you may ask? Well, there's a certain Chaos God...