Viridian Betrayers

Viridian Betrayers has infect as long as an opponent is poisoned. (It deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)

Vapor Snag

Return target creature to its owner's hand. Its controller loses 1 life.

Tezzeret's Gambit

({U/P} can be paid with either {U} or 2 life.)
Draw two cards, then proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

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.

Mutagenic Growth

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

Forest

Island

Gitaxian Probe

({U/P} can be paid with either {U} or 2 life.)
Look at target player's hand.
Draw a card.

Viral Drake

Flying
Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
{3}{U}: Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Spinebiter

Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
You may have Spinebiter assign its combat damage as though it weren't blocked.

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.)