The bug
Undead mobs in custom dimensions do not catch fire from daylight (even if skylight is set to true). Worldgen file attached for reproduction, dimension id is chromakey:sky.
Undead mobs in custom dimensions do not catch fire from daylight (even if skylight is set to true). Worldgen file attached for reproduction, dimension id is chromakey:sky.
Probably related to this, spiders in custom dimensions seem to always be neutral.