To clarify aflatoxin stacks to a creatures poison damage by +2 damage per attacking turn, and upon death, with a few exceptions, such as a virus sacrificing itself, a malignant cell will take it's place. Each cell has an ability called infest, infest means another malignant cell will spawn in a free spot. When a malignant cell spawns, it automatically attacks if it can. Malignant cells are 1/1 creatures. There is a maximum of 23 creature slots.
Aflatoxin has all sorts of utilities, use it as creature control to prevent opponents of playing other cards.
Combined with a shield blocking 1 damage, this prevents your opponent from damaging you, especially if you have creature control cards or abilities.
Combined with SoPa you can buff a large army on your side of the field with little cost.
Against players not using a shield, allow it to quickly produce a wienie army.
Combined with graveyards or condors, and an AoE, use it to setup mass skeleton production or pumped up condors.
Use it as for big creature control, such as played on a Ruby Dragon.
Use it on your creatures if opponent is using bonewalls, to quickly take down bonewalls.