"Dark Brotherhood also accepts vampires as a Dark Brother or Dark Sister. However, in 3E 421, some of the vampires within the guild, formed a group called the Crimson Scars and plan to end the rule of the non-vampire Black Hand. They will then put vampires as the members of the Black Hand. Their plan was thwarted; the members of the vampiric group were slaughtered in their sleep. The leader of the group, Greywyn, was managed to escape the massacre." - Imperial Library
So I'm thinking, what if this Greywyn guy is still alive and kicking and hes planning on getting revenge on the Dark Brotherhood for thwarting his plans? What if this is the rival Assassins Guild in Skyrim? Thoughts?