Mutants are divided into 2 types
People
Animals
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‎People
‎People are just zombies, only under the influence of parasites. When a person dies, their bodies are often used by parasites for food. And the so-called roots stretch all the way to the brain. It may be that a person lacks important organs inside, but the parasite only cares that the person can walk, and the rest doesn't matter. The purpose is to reproduce, of course, and not just settle on a single corpse. These walking corpses are known as mutants or, more commonly, zombies.
Animals
‎It's much more interesting here. If people are just zombies who prevent you from surviving in a not-so-lovely world, then animals... Yes, they attack, and yes, they can be killed, but they have a greater significance. You can read about each animal in the encyclopedia and notes after studying them. Animals in the ring can also lead you to other branches of events, depending on how you treated them: Did you feed Reger? He will remember and may not attack next time. Did you kill the bear cubs of the mother bear? Well... Good luck surviving