Cavern Wyvern

Sunlight Sensitivity. While in sunlight, the bat wyvern has disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight.

Blind Senses. The Cavern wyvern can't use its blindsight while deafened and unable to smell.

Cave Dweller. This creature lives in a little to no light environment and since has adapted to no longer need eyes, due to this the creature gains blindsight and tremorsense, along with a plus 3 to passive perception, and a boost in dexterity.

Innate Spellcasting. The Cavern wyvern spellcasting ability is Wisdom (spell save DC 13). It can innately cast the following spells, requiring no material components:

At will: poison spray

1/day each: darkness, hold person

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.

Sound Burst. The wyvern let's out a skull-splitting screech each player within a 50ft cone must succeed on a DC 13 Constitution saving throw, taking 4 (2d4 +1) physic damage, plus 11 (2d6 +4), thunder damage on a failed save and half as much on a successful one.