Zeke Yeager, Titanshifter

Zeke Yeager, Titanshifter enters the battlefield
with a +1/+1 counter on it.
{1}{r}{g}: Put a +1/+1 counter on Zeke Yeager,
Titanshifter, then Regenerate it.
At the beginning of each end step if Zeke Yeager,
Titanshifter has four or more +1/+1 counters,
transform it.