Hydreigon (5e Creature)
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Medium dragon, any alignment
Hustle. Once per turn, before the hydreigon makes a melee attack, it can choose to take a -5 penalty to the attack roll. If the attack hits, it add +10 to the attack's damage.
Multiple Heads. The hydreigon has advantage on saving throws against being blinded, deafened, stunned, or knocked unconscious.
Wakeful. While the hydreigon sleeps, at least one of its heads is awake.
Seething. Once it enters combat, the hydreigon deals 10 piercing damage to itself at the end of its turn if it did not make an attack on that turn. This damage ignores resistance, and it cannot reduce the hydreigon to 0 hit points.
Magic Weapons. The hydreigon's weapon attacks are magical.
Multiattack. The hydreigon makes two bite attacks and one dark pulse attack.
Bite. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 9 (1d8 + 5) piercing damage plus 7 (2d6) necrotic damage.
Dark Pulse. The hydreigon shoots a blast of darkness in a 30-foot radius around it. Each creature of the hydreigon's choice in that area must make a DC 17 Constitution saving throw, taking 18 (4d8) necrotic damage on a failed save, or half as much damage on a successful one.
Bite Back. In response to being hit with a melee attack, the hydreigon makes one Bite attack against the attacker