I do not know how to code (especially for a complex game like RAIN WORLD), but some enemy ideas that I HAVE TO SEE are:

Scavwalker: a arthropod that can mimic scavengers, the antlers are mandibles, the back hairs are legs, and the arms are antennae, it would be able to get off its back which allows it to walk around and act like a scavenger, it can carry tools but never uses them, and will often travel with scavengers, it will try to get a scavenger alone to kill and eat it, if you kill a scavwalker you will get a lot of good reputation from scavengers but scavwalkers will hunt you down, they can be tamed by feeding them scavengers, they were made by Five Pebbles to help get rid of scavengers in Metropolis, but they migrated into other regions as well
Hippofly: neutral giant batfly relatives, they are common place in ecosystems high above the clouds, they usually won't attack however have 5 giant "green fruits" hanging from their belly, if hit with a spear it will drop maggots which can be eaten for 2 food pips (only 1 pip for carnivorous slugcats), but the hippofly will try to grab you before dropping you into pits
Vulture mimic: a bronze colored lizard that is extremely weak, it can only hunt small prey such as scugs and batflies, but when it sees a creature that can harm or kill it the vulture mimic will make vulture sound and flash a vulture mask like pattern on its head to scare away threats, if that doesn't work it can climb up walls to escape
Draggers: a species of tiny spider that is found in dark regions where it sneaks up on slugcats, scavengers, and lantern mice, it will than steal any light source they have (sometimes stealing the creature itself) and using them to scare off other spiders that will often eat it