Multiattack. The wyvern makes two attacks: one with its bite and one with its stinger. While flying, it can use its claws in place of one other attack.

Bite. Melee Weapon Attack: +7 to hit, reach 10 ft., one creature. Hit: 11 (2d6 + 4) piercing damage.

Stinger. Melee Weapon Attack: +7 to hit, reach 10 ft., one creature. Hit: 11 (2d6 + 4) piercing damage. The target must make a DC 15 Constitution saving throw, taking 24 (7d6) poison damage on a failed save, or half as much damage on a successful one.

Poison Breath (Recharge 5-6): The dragon exhales poisonous gas in a 60-foot cone. Each creature in that area must make a DC 18 Constitution saving throw, taking 56 (16d6) poison damage on a failed save, or half as much damage on a successful one.

Desiccating Breath (Recharge 5–6): The dragon exhales yellowish necrotic energy in a 90-foot cone. Each creature in that area must make a DC 20 Constitution saving throw. On a failed save, the creature takes 49 (14d6) necrotic damage and is weakened until the end of its next turn. A weakened creature has disadvantage on Strength-based ability checks and Strength saving throws, and the creature's weapon attacks that rely on Strength deal half damage. On a successful save, the creature takes half as much damage and isn't weakened.

Claws. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) slashing damage.