Rofellos, Llanowar Emissary

{t}: add {g} or {u} to tour mana pool. Spend
this mana only to cast a creature spell.

Whenever you play a green creature spell,
if {u} was spent to cast this spell, you may
search your library for a green or blue
creature card and reveal it. If you do shuffle
your library and put that card on top of it.