In recent months, as The Talon of Horus rolls ever onward, I've spilled a wealth of words on Ezekyle Abaddon and the Black Legion over emails and hastily-chucked notes to various other authors and IP-tastic souls in the dark conclave of Those Who Contribute to 40K.
This is a difficult book, not only because of the wealth of lore (much of which subtly shifts from edition to edition, meaning you need to choose what to focus on and run with that), but also because of the 40K comedy memes that do the rounds, just like in any fandom.
So. Much. Awesome.