Enduring Hydra

Extremist X - {x}{g}{g} (You may cast this spell for its extremist cost. If you do, it deals X damage to you.)
Defiance (Whenever this creature attacks, if
defending player controls an untapped creature with
greater power, put a +1/+1 counter on this creature.)
Enduring Hydra enters the battlefield with X
+1/+1 counters on it. If X is 5 or more, you may
put a reach and/or trample counter on it.