Professor Caleb Widogast

Mentor (Whenever this creature attacks, put a
+1/+1 counter on target attacking creature with
lesser power.)
When Caleb enters the battlefield, summon a 1/1
Frumpkin.
{g}{g}{r}: polymorph into a 6/6 T-Rex with
Trample until the end of the turn. If T-Rex
would be put into a graveyard, revert to
Caleb instead.