Poisoned Song

Corrupt Song (This card casts {1} less to cast for
every choir card in your graveyard)
Deathtouch, Infect, Choirbane
Every vampire creature is a choir in addition to
its creature types, and each choir creature is a
vampire in addition to its creature types.
Whenever a choir leaves the battlefield, Proliferate(activate this ability only on your turn, and only once per turn)