Ancient Wyvern

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: +10 to hit, reach 10 ft., one creature. Hit: 13 (2d6 + 6) piercing damage.

Claws. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 15 (2d8 + 6) slashing damage.

Stinger. Melee Weapon Attack: +10 to hit, reach 10 ft., one creature. Hit: 13 (2d6 + 6) piercing damage. The target must make a DC 17 Constitution saving throw, taking 24 (7d6) poison damage on a failed save, or half as much damage on a successful one.

The wyvern can take three legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The wyvern regains spent legendary actions at the start of its turn.

Detect. The wyvern makes a Wisdom (Perception) check.

Bite. The wyvern makes a bite attack.

Sting (Costs 2 Actions). The wyvern attacks with its stinger.

Wing Attack (Costs 2 Actions). The wyvern beats its wings. Each creature within 15 feet of the wyvern must succeed on a DC 18 Dexterity saving throw or take 13 (2d6 + 6) bludgeoning damage and be knocked prone. The wyvern can then fly up to half its flying speed.