The Undead Ur-Dragon

Flying, Trample
Sacrifice a creature: put a +1/+1 counter on The
Undead Ur-Dragon.
Sacrifice a Dragon: put two +1/+1 counters on
The Undead Ur-Dragon.
Sacrifice an Elder Dragon: put three +1/+1
counters on The Undead Ur-Dragon.
Sacrifice an Elder Dragon Legend: put five +1/+1 counters on The Undead Ur-Dragon.