Miasma Aura. Miasma radiates from the cat in an aura with a 30-foot radius. The aura moves with it, centered on it. Each hostile creature in the aura takes (1d6) necrotic damage once per turn when it moves into the aura or starts its turn in it.
Devil's Sight. Magical darkness doesn't impede the devil's darkvision.
Magic Resistance. The devil has advantage on saving throws against spells and other magical effects.
Multiattack. The devil makes three melee attacks: one with its bite and two with its claws. Alternatively, it can use Hurl Miasma twice.
Claw. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 6 (1d6 + 3) piercing damage.
Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 3) bludgeoning damage.
Hurl Miasma. Ranged Spell Attack: +7 to hit, range 150 ft., one target. Hit: 10 (3d6) necrotic damage.
The Devil can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The Devil regains spent legendary actions at the start of its turn.
Claws. The Devil makes one attack with its Claws.
Invoke Fear (Costs 3 Actions). The Devil focuses on one creature it can see within 60 ft. it must succeed on a DC 14 Wisdom saving throw or be Frightingend until the end of its next turn.
Miasma Pulse (Costs 2 Actions). The Devil invokes sends a pulse of strong miasma outwards, alls creatures with 30 feet must succeed on a DC 13 Constitution saving throw or take (2d6) necrotic damage.