Daboil, Dark World of Mystery

Daboil enters the battlefield tapped.
{t}: Add {u} or {b} to your mana pool.
{u}{b}{t}: You may cast target instant or sorcery
from your graveyard, put spells resolved this way
on the bottom of your library instead of your graveyard.
"A world like no other..." - Larris, Horde Empress