Octomer

Devourmorph — 8 (You may cast this card face
down as a 2/2 creature for {3}. Turn it face up any
time by sacrificing eight creatures and put eight +1/+1 counter on it.)
As long as Octomer has a +1/+1 counter on it,
it's an Octopus in addition to its other types, and
it can block an additional creature for each +1/+1 counter on it.