Ivysaur

Evolve {1}{g}— If you control a Bulbasaur, you may place this card from your hand on top of it at any time you could cast a creature spell.
{t}Add {g} to your mana pool; if this creature was evolved, add {g}{g} instead.
Whenever this creature becomes tapped, each opponent loses 1 life, and you gain 1 life.