Cave Wyvern

Keen Hearing and Smell. The Cave Wyvern has advantage on Wisdom (Perception) checks that rely on hearing or smell.

Stone Camouflage. The Cave Wyvern has advantage on Dexterity (Stealth) checks made to hide in rocky terrain.

Echolocation. The hook horror can't use its blindsight while deafened.

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 + 7) piercing damage.

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

Stinger. Melee Weapon Attack: +7 to hit, reach 10 ft., one creature. Hit: 11 (2d6 + 7) piercing damage. The target must make a DC 16 Constitution saving throw, taking 29 (9d6 +2) poison damage on a failed save, or half as much damage on a successful one.

Sound Burst. The wyvern let's out a skull-splitting screech each player with in a 50ft cone you must succeed on a DC 15 constitution saving throw, taking 6 (2d4 +2) physic damage, plus 11 (3d6 +2), thunder damage on a failed save and half as much on a successful one.