Micros can only reproduce while inhabiting a living organism, and it appears as though zoans are their only viable hosts. When a zoan becomes the unwilling host to a swarm of micros, they fall ill to an ailment now known as “microblight.”

Microblight is completely undetectable until the later stages, wherein the infected will assimilate a nearby inanimate object, transforming them into a “blight beast.” It is believed that the micros are somehow able to “tap in” to the infected’s bestial ancestry, resulting in extremely dangerous feral creatures.

Blight beasts can be cured, but must be beaten into submission by ARMS Wielders, leaving them exhausted and vulnerable, allowing the Wielders to extract the micros. The cured zoans are often in a weakened state afterwards, but recover normally, and have no memory of their time as a beast.