Phase spider

Phase spiders are a giant arachnid monstrosities that originate from the Ethereal Plane and can transport from Ethereal to Material Plane at will.

Abilities

 * Senses: Darkvision.
 * Bite: The phase spider can make a bite attack that deals piercing damage and additional poison damage (conditional on a saving throw).
 * Ethereal Jaunt: The phase spider can move between the ethereal plane and the material plane in either direction as a bonus action.

Known Phase Spiders
Mighty Nein encountered a phase spider in the sewers of Zadash.