Magic Resistance. The spiderdragon has advantage on saving throws against spells and other magical effects.

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

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

Multiattack. The spiderdragon makes one Bite attack and two Claw attacks.

Bite. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit:10 (1d10 + 5) piercing damage plus 13 (2d12) poison damage.

Claw. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit:12 (2d6 + 5) slashing damage.

Spiderling Breath (Recharge 5–6). The spiderdragon exhales venomous spiderlings in a 30-foot cone. Each creature in that area must make a DC 15 Dexterity saving throw, taking 33 (6d10) piercing damage and 33 (6d10) poison damage on a failed save or half as much damage on a successful one.

Stifling Webs (Recharge 5–6). The spiderdragon spins a 30-foot cube of strong, sticky webbing in an area adjacent to itself. The webbing lasts for 1 minute, is difficult terrain, and lightly obscures its area. A creature that starts its turn in the webbing or enters the webbing for the first time on its turn must succeed on a DC 15 Dexterity saving throw or have the restrained condition while in the web. As an action, a creature can free itself or another creature from the web by succeeding on a DC 15 Strength check.

A 5-foot cube of the web is destroyed if it takes at least 10 acid, fire, or slashing damage on a single turn.