I heard that these guys were based off of the Xenomorphs from the Alien franchise, and it definitely makes sense. Get impregnated by a queen, have a horrifying chestburster emerge and try to kill you? Seems pretty familiar!
Since i cant find this anywhere. Reapers take reduced damage naturally so its a good soaker. Dont bring light pets near theese because they take more damage and deal less damage.The reaper burns when light is near it. Nameless will attack it tho. Sorry for bad english.
Don't use admin commands to summon a wild subterranean reaper king. I did on my single player world, and now I have an invincible reaper king with no level count running around the boss terminal. Kill command and even the admin rifle's destroy function do nothing to it, and attempting to forcetame it crashes the game. This may be a problem