Primeval Swarm

All Forests and all Saprolings are 1/1 green Saproling creatures and Forest lands in addition to their other types. (They're affected by summoning sickness.)

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for or one mana of that creature's color.) Buyback (You may pay an additional as you cast this spell. If you do, put this card into your hand as it resolves.) Create a 1/1 green Saproling creature token.

Whenever you cast a creature spell, create a 3/3 green Beast creature token. Whenever you cast a noncreature spell, put three +1/+1 counters on target creature you control. Landfall — Whenever a land you control enters, you gain 3 life.