Forgotten Wreath

Forgotten Wreath enters the battlefield tapped.
Whenever a creature you control is removed from the battlefield, add {w}{u}{g} to your mana pool. Then you may pay {x}, where X is that creatures converted mana cost. If you do return it to your hand at the beginning of the next end step.
{t}: Add {w}, {u} or {g} to your mana pool.