Zel'dovan, The Dream Nexus

At the beginning of each of your main phases,
add two mana in any combination of {g}, {w}, or {u}. Spend this mana only to cast creature spells.
Whenever a creature enters the battlefield
under your control, choose a creature type.
That creature is the chosen type in addition
to its other types.
Zel'dovan: where dreams come to live away from the plagues of nightmares we face.