Atropos the nightmare elemental

Frightful presence. At the beginning of the encounter all other creatures (even if they should be allied with Bane) have to succeed on a 16 CHA saving throw or be frightened of Bane. Affected creatures can repeat the saving throw on the end of their turns.

Bane can also end the effects of Nightmare and Fiend's Grip at will.

Action Ranged Attack. RangedWeapon Attack: +8 to hit, range 30 ft., 1 target. Hit: 10 (1d10 + 5) [necrotic] damage. On hit the creature must succeed on a DC 16 WIS saving throw or be frightened until the end of Bane's next turn.

Nightmare. Bane traps the target in its worst nightmare. They must succeed on a 18 WIS saving throw. On a success the target is not affected by the ability. However it gains disadvantage for the next saving throw against Nightmare. If the target fails its saving throw it will fall asleep, writhing in pain and nightmarish visions. On their turn they will suffer 10 (1d10 + 5) necrotic damage. There is no saving throw against the damage or the sleep affect. They will automatically wake up after 3 turns or if damaged by another creature (excluding Bane). The attacking creature must then succeed on a 18 WIS saving throw or suffer from the abilities effects for the remainder of its duration or until it is attacked...

Fiend's Grip. CONCENTRATION Bane graps his target with a spectral hand, disabling it. The creature must succeed on a 18 WIS saving throw. If it succeeds it takes 21 (2d10 + 10) cold damage and healing effects on the creature are halved until the end of its next turn. If the target fails its saving throw it is stunned. On its turn the creature will take 21 (2d10 + 10) cold and 21 (2d10 + 10) necrotic damage. It will also lose a 1st level spell slot. On continuous turns Bane can use its Action to apply the damage effect again, the creature will however only lose a spell slot if it takes damage from Fiend's Grip on its own turn. For each continuous round the level of the spell slot lost increases by 1. If the creature doesn't have a spell slot left at the level it will instead lose a spell slot of the next higher level. Bane has advantage on concentration checks for Fiend's Grip. Bane has to recharge this ability. On the beginning of his turn he may roll a d6. On a 5 or 6 he will recharge the use of Fiend's Grip.

Enfeeble. Shoots a tendril of fear at the target. It must succeed on a 16 CON saving throw. On a success the creature resists the effect completely. On a failure it will lose its will to fight the nightmare elemental. All its damage from weapon attacks will only deal half damage and the range of spells and abilities is reduced by one third. The creature can attempt another saving throw on the end of its turn.

Shield. Once for every spell slot destroyed Bane can use the Shield spell as a reaction. Shield will increase his AC by +5 until the start of his next turn.

Bane has 1 legendary action.

Brain Sap. 15 ft. range, + 10 to hit, 1 target. Hit: Bane feeds on the vital energies of the target. On hit he will deal 26 (3d10 + 10) necrotic damage to the target and heal for same amount. The targets healing is halved until the start of its next turn.