Godrick, the Grafted

Reach, double strike, menace
Graft {1}{b}{g}(Whenever this creature kills another creature, you may pay its graft cost. If you do, exile
that creature. This creature gets +X/+X where X is
the exiled creature's power.)
{t}, {1}{r}{g}, Remove X +1/+1 counters from
Godrick, the Grafted: Godrick, the Grafted deals
X damage to one target. Target creature gets
+X/+X.
"Forefathers, one and all. Bear witness!"