A motionless mineshaft NPC that is actually a doorway to the Skinwalker variants.
DarkIn303 spawns in mineshafts near rails, cobwebs or plank blocks, completely without AI and motionless.
Approaching within 5 blocks makes it vanish and summon a Mineshaft Skinwalker in its place, it functions as a gateway into the Skinwalker variants rather than a threat of its own.