Shapechanger. The giant spider mimic can use its action to polymorph into an object or back into its true, spider form. Its statistics are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Adhesive. The giant spider mimic adheres to anything that touches it. A gargantuan or smaller creature adhered to the mimic is also grappled by it (escape DC 17). Ability checks made to escape this grapple have disadvantage.

Grappler. The giant spider mimic has advantage on attack rolls against any creature grappled by it.

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

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

Multiattack. The giant spider mimic makes can make up to four pseudopod attacks and one bite attack.

Pseudopod. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 10 (1d10 + 5) bludgeoning damage. The target is subjected to its Adhesive trait.

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 7 (1d8 + 3) piercing damage plus 4 (1d8) acid damage, and the target must make a DC 11 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.

Web (Recharge 5–6). Ranged Weapon Attack: +5 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 17 Strength check, bursting the webbing on a success. The webbing can also be attacked and destroyed (AC 10; hp 5; immunity to bludgeoning, poison, acid, and psychic damage).