Undying Giant Spider

Spider Climb. The 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 spider knows the exact location of any other creature in contact with the same web.

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

Undying Resurrection. When an Undying Giant Spider is reduced to 0 Hit Points its body begins to disintegrate over a period of 1 minute. In 2d6 hours the Giant Spider will regenerate in a random area within the plague area where it was created. 

Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one creature. Hit: 13 (2d8 + 4) piercing damage, and the target must make a DC 12 Constitution saving throw, taking 9 (2d8) 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.

Acidic Web (Recharge 5–6). Ranged Weapon Attack: +7 to hit, range 30/60 ft., one creature. Hit: The target is restrained by webbing. At the start of a creature's turn, if it is trapped in the webbing, it much succeed on a DC 12 Constitution saving throw. The creature takes 9 (2d8) acid damage on a failed save, or half as much damage on a successful one. As an action, the restrained target can make a DC 13 Strength check, bursting the webbing on a success. The webbing can also be attacked and destroyed (AC 10; hp 5; vulnerability to fire damage; immunity to bludgeoning, poison, and psychic damage).