it's really annoying not being able to start a game for a whole hour without it spawning and completely ruining the run.
that or at least make it killable with starter gear, because so far the only way i was able to kill it was by cheating in a crumble earth wand and going underground.
also the first time i saw it, it did spook me, so i guess goal accomplished?

in the meantime, i've manually disabled spawning, for those who want to do the same, go into your steam installation and navigate to the folder ./steamapps/workshop/content/881100/2910427839
then in init.lua, comment out the line EntityLoad( "data/entities/animals/nightmare_monster.xml", -666, 0 ) by adding two dashes in front of it. (as of writting it is on line 236)