Black Wyvern

Black Magic.  This variant of Wyvern has been infused with the Black Magic of an Ancient Black Dragon giving it black scales, higher Intelligence, and a breath weapon.

Draconic Language. Can read and understand Draconic but cannot speak it unless spoken to with telepathy. 

Ritual Backlash. This creature has -2 penalty on all ability checks and saving throws. (1d4+1 days)

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: +5 to hit, reach 10 ft., one creature. Hit: 11 (2d6 + 4) piercing damage.

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

Stinger. Melee Weapon Attack: +5 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) acid damage on a failed save, or half as much damage on a successful one.

Acid Breath (Recharge 5–6). The wyvern exhales acid in a 30­-foot line that is 5 feet wide. Each creature in that line must make a DC 14 Dexterity saving throw, taking 49 (11d8) acid damage on a failed save, or half as much damage on a successful one.