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

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

Frightful Presence. Each creature of the Boltreaver Wyvern's choice that is within 120 feet of the Boltreaver Wyvern and aware of it must succeed on a DC 16 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the Boltreaver Wyvern's Frightful Presence for the next 24 hours.

Lightning Breath (Recharge 5–6). The Kingslayer Wyvern exhales lightning in a 60-­foot line that is 5 feet wide. Each creature in that line must make a DC 18 Dexterity saving throw, taking 54 (10d8) acid damage on a failed save, or half as much damage on a successful one.

Legendary Resistance (2/Day). If the Kingslayer Wyvern fails a saving throw, it can choose to succeed instead.