Multiattack

The wyvern attacks once with its bite and once 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 target. Hit: 13 (2d8 + 4) piercing damage.

Claws

Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 9 (2d4 + 4) slashing damage. If the wyvern is attacking from above the target is grappled by the wyvern (escape DC 15). While grappling a target in this way the wyverns Speed is reduced to 0 it can't use its claws to attack any other creature and it has advantage on attacks against the target.

Stinger

Melee Weapon Attack: +7 to hit, reach 10 ft., one creature. Hit: 11 (2d6 + 4) piercing damage. The target makes a DC 15 Constitution saving throw taking 24 (7d6) poison damage on a failure or half damage on a success.