Unearth

Return target creature card with mana value 3 or less from your graveyard to the battlefield.
Cycling {2} ({2}, Discard this card: Draw a card.)

Ravenous Rats

When Ravenous Rats enters, target opponent discards a card.

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)

As an additional cost to cast this spell, sacrifice a land.
Search your library for a land card, put that card onto the battlefield, then shuffle.

When Phyrexian Rager enters, you draw a card and you lose 1 life.

Sacrifice Spore Frog: Prevent all combat damage that would be dealt this turn.

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
{G}: Regenerate River Boa.