Venom Connoisseur

Alliance — Whenever another creature you control enters, this creature gains deathtouch until end of turn. If this is the second time this ability has resolved this turn, all creatures you control gain deathtouch until end of turn.

Venom

Enchant creature
Whenever enchanted creature blocks or becomes blocked by a non-Wall creature, destroy the other creature at end of combat.

Skithiryx, the Blight Dragon

Flying
Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
{B}: Skithiryx gains haste until end of turn.
{B}{B}: Regenerate Skithiryx.

Venom Blast

Put two +1/+1 counters on target creature you control. It deals damage equal to its power to up to one other target creature.

Sisay, Weatherlight Captain

Sisay gets +1/+1 for each color among other legendary permanents you control.
{W}{U}{B}{R}{G}: Search your library for a legendary permanent card with mana value less than Sisay's power, put that card onto the battlefield, then shuffle.