Vigilance, reach

At the beginning of combat on your turn, choose a creature type, then amass 1 of that creature type.

Ben get's +1/+1 for each creature type on an army you control.

{3}{G}{B}{U}: Exile Ben and return it to the battlefield transformed. Do this only if you control a creature with 3 or more creature types. (Pretend I came up with the other side before this.)