Phase Spider

   Habitats          
Size: Large
Type: Magical Beast
Form: arachnid
Temper: predatory
# App: 1d6
Lair:
Diet:
Combat Dice: 0
Hit Points: 25 + 1d10
Attack Rank: 0
Passive Defense: 0
Active Defense:
Damage Reduction: 0
Role: skirmisher
Ground:
Climb/Arboreal:
Flight:
Swim:
Benthic:
Burrow:
Ethereal:
Actions/Abilities/Traits: (D&D 5e)
Actions/Abilities/Traits: (d20)
Actions/Abilities/Traits: (OSR)
Actions/Abilities/Traits: (Pathfinder 1e)

A phase spider possesses the magical ability to phase in and out of the Ethereal Plane. It seems to appear out of nowhere and quickly vanishes after attacking. Its movement on the Ethereal Plane before coming back to the Material Plane makes it seem like it can teleport.

5e SRD