Tiamat of the NineHells

Shroud, Indestructible, Flying, Trample.
{w}{u}{b}{r}{g}, destroy up to five target Creatures.
Tiamat of the NineHells' Power is equal to the
number of Dragon and/or "Cultist of the
Dragon" Creatures you control.
You must control at least five Creatures named "Cultist of the Dragon" to cast this card from
your hand. If you would ever have no Creatures
named "Cultist of the Dragon" on your side of
the Field, Exile Tiamat of the NineHells.