Counterspell

Titanic Growth

Target creature gets +4/+4 until end of turn.

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.

Forest

Blanchwood Armor

Enchant creature
Enchanted creature gets +1/+1 for each Forest you control.

Beast Within

Destroy target permanent. Its controller creates a 3/3 green Beast creature token.

Island

Corrupted Resolve

Counter target spell if its controller is poisoned.

Contentious Plan

Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)
Draw a card.

Mutagenic Growth

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