Dimhollow, Crypt of Seclusion

Dimhollow, Crypt of Seclusion enters the battlefield tapped unless you tap 1 non-token
Vampire creature you control.
{t} Add {b}{r} to your mana pool.
Spend this mana only to cast Vampire
creature spells.
During your end step, if you control three or
more non-token Vampire creatures you may
transform Dimhollow, Crypt of Seclusion.
Dimhollow was left to ruin in the absence of the
Volkihar vampires, but in recent times...