Mixedmen are creatures in Parasite Eve. It is a disgusting NMC that is only encountered a few times throughout St. Francis Hospital. It is hard to tell what this NMC came from because of how deformed it is, but given the name, it is possible Eve melted humans together, presumably the patients, doctors and nurses at the hospital.
One of the primary attacks of the Mixedmen is to release a ball. It can release up to three balls at a time. These balls bounce around the room at random angles and will damage Aya by slamming into her. If one of the balls is destroyed the Mixedmen will create a new one. The best tactic is to avoid the balls and go for the main body because if you kill the Mixedmen all of the balls will disappear.
When the Mixedmen has released all three balls it will then produce a loud cry which has a huge radius. This cry will cause a large amount of damage to Aya and will also cause stiffness. Since the area of attack is so large it is hard to dodge so the best thing to do is counter the effects with a Cure-M and healing.