Island

Might of Old Krosa

Target creature gets +2/+2 until end of turn. If you cast this spell during your main phase, that creature gets +4/+4 until end of turn instead.

Blighted Agent

Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
Blighted Agent can't be blocked.

Invigorate

If you control a Forest, rather than pay this spell's mana cost, you may have an opponent gain 3 life.
Target creature gets +4/+4 until end of turn.

Glistener Elf

Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)

Forest

Scale Up

Until end of turn, target creature you control becomes a green Wurm with base power and toughness 6/4.
Overload {4}{G}{G} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Snakeskin Veil

Put a +1/+1 counter on target creature you control. It gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)

Snapback

You may exile a blue card from your hand rather than pay this spell's mana cost.
Return target creature to its owner's hand.

Mutagenic Growth

({G/P} can be paid with either {G} or 2 life.)
Target creature gets +2/+2 until end of turn.

Distortion Strike

Target creature gets +1/+0 until end of turn and can't be blocked this turn.
Rebound (If you cast this spell from your hand, exile it as it resolves. At the beginning of your next upkeep, you may cast this card from exile without paying its mana cost.)

Slaughter Pact

Destroy target nonblack creature.
At the beginning of your next upkeep, pay {2}{B}. If you don't, you lose the game.