Chained Demon

Magic Resistance. The Chained Demon has advantage on saving throws against spells and other magical effects.

Broken Chains. Any caster brave enough to cast knock or dispel magic  on a Chained Demon can remove the creature’s shackles/chains if they make a spell save DC15, if they fail, any further attempts to cast knock or dispell magic on the demons chains fail automatically for the next 24 hours. If they succeed on the spell save dc the chains break off and the demon is no longer under control of whoever put the magical chains on it. the DM decides the further behaviour/actions of the demon when this happens.  

Multiattack. The Chained Demon uses Horror Nimbus if it can. It then makes two attacks: one with its bite and one with its claws.

Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 32 (5d10 + 5) piercing damage.

Claw. Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 15 (3d6 + 5) slashing damage.

Horror Nimbus (Recharge 5–6). The Chained Demon magically emits scintillating, multicolored light. Each creature within 15 feet of the nalfeshnee that can see the light must succeed on a DC 15 Wisdom saving throw or be frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the demons Horror Nimbus for the next 24 hours.