Ancient Giant Phase Spider

Spider Climb. The ancient phase spider can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Web Sense. While in contact with a web, the ancient phase spider knows the exact location of any other creature in contact with the same web.

Web Walker. The ancient phase spider ignores movement restrictions caused by webbing.

Multiattack: The ancient phase spider can make three attacks on its action, any combination of bite, leg or web attacks can be used.

Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one creature. Hit: 13 (2d8 + 4) piercing damage, and the target must make a DC 15 Constitution saving throw, taking 18 (4d8) poison damage on a failed save, or half as much damage on a successful one. If the poison damage reduces the target to 0 hit points, the target is stable but poisoned for 1 hour, even after regaining hit points, and is paralyzed while poisoned in this way.

Leg.  Melee Weapon Attack: +8 to hit, reach 10ft., one creature per leg.   Hit: 17 (3d8+4) bludgeoning damage, and the target must make a DC 12 Dexterity save or be knocked prone.

Web (Recharge 4–6). Ranged Weapon Attack: +10 to hit, range 30/60 ft., one creature. Hit: The target is restrained by webbing. As an action, the restrained target can make a DC 16 Strength check, bursting the webbing on a success. The webbing can also be attacked and destroyed (AC 14; hp 20; vulnerability to fire damage; immunity to bludgeoning, poison, and psychic damage).

Ethereal Jaunt. As a bonus action, the ancient phase spider can magically shift from the Material Plane to the Ethereal Plane, or vice versa.