Bloated Contaminator

Trample
Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)
Whenever Bloated Contaminator deals combat damage to a player, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Grist, the Plague Swarm

+1: Create a 1/1 black and green Insect creature token, then mill two cards. Put a deathtouch counter on the token if a black card was milled this way.
−2: Destroy target artifact or enchantment.
−6: For each creature card in your graveyard, create a token that's a copy of it, except it's a 1/1 black and green Insect.

Grist, Voracious Larva

Deathtouch
Whenever Grist, Voracious Larva or another creature you control enters, if it entered from your graveyard or you cast it from your graveyard, you may pay {G}. If you do, exile Grist, then return it to the battlefield transformed under its owner's control.