Wyvern

Large dragon, unaligned

Armor Class 13 (natural armor)
Hit Points 110 (13d10 + 39)
Speed 20 ft., fly 80 ft.

Skills Perception +4
Senses darkvision 60 ft., passive Perception 14
Languages —
Challenge 6 (2,300 XP)

Actions

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.