Durdle Turtle

Defender
{g/u}{g/u}{g/u}{g/u}: Exile Durdle Turtle with any number
of durdle counters. At the beginning of combat
on your turn, if Durdle Turtle has durdle
counters on it, remove a counter. When the last
durdle counter is removed, put Durdle Turtle
onto the battlefield under your control and
double its power for each durdle counter
removed. It gains haste and trample and can
attack as if it didn't have defender.