Precursor Blast Droid

The precursor waterbot (im not even joking) is a walker type enemy that spawns mostly on precursor minibiomes and is guaranteed to spawn in multiple parts of the precursor ruins mission. It tends to "sprinkle" radioactive energy orbs very randomly in the upwards direction, usually hitting nothing, as is expected of a waterbot.

It is immune to liquid nitrogen, pus, insanity, bio-ooze, poison debuff, recuperates from knockback 75% faster, is 33% more resistant to knockback and has a base protection of 0.25. It deals 10 (slash, physical) base damage on contact.

Drops
Drops the normal robot treasure.

Fighting
Laugh at its sheer impotence and then consequently shoot it.