Bepis

Shapechanger. The fiend can use its action to polymorph into a Small or Medium humanoid, or back into its true form. Without wings, the fiend loses its flying speed. Other than its size and speed, its statistics are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Bloodlust. After killing an enemy gains advantage on all its attacks until the end of the encounter. All enemies gains advange against it.

Nightmare. At will, the fiend can enter into a humanoid's dream, the humanoid can make a DC 15 Wisdom saving throw, to resist. For the purpose of this weapon, "humanoid" refers to any creature with the humanoid type.

The nightmare lasts as many minutes as the creature's Wisdom score, at the end of it, the creature dies.

During the nightmare, the humanoid moans, sweats and flinches; any ally can try to wake the creature( DC 15 Wisdom saving throw) but only once.

Spells like: antimagic field, bless, death ward, hallow, magic circle, protection from evil... can prevent a nightmare. Casting these on an affected creature immediately ends the nightmare.

The fiend can end the nightmare at will; if it does, it appears beside the affected creature.

If the nightmare is forced to end by spell of waking up the creature, the fiend appears beside the affected creature and is stunned until the end of turn.

Claw (Fiend Form Only). Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 6 (1d6 + 3) slashing damage.

Sweet bloodletting glaive. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 8 (1d10 + 1) slashing damage.

When you hit a creature with this magic weapon, that target must succeed on a DC 10 Strength saving throw or be stunned until the end of your next turn, if this target isn't a construct or an undead you also gain 2 temporary hit points.

Dance of blades: The fiend uses a full action to make a melee Attack against any number of creatures within its reach, with a separate Attack roll for each target.

She came from behind(Recharge 4–6). The fiend magically teleports, up to 40 feet to an unoccupied space it can see. Before or after teleporting, the fiend can make one melee attack.

Charm. One humanoid the fiend can see within 30 feet of it must succeed on a DC 15 Wisdom saving throw or be magically charmed for 1 day. The charmed target obeys the fiend's verbal or telepathic commands. If the target suffers any harm or receives a suicidal command, it can repeat the saving throw, ending the effect on a success. If the target successfully saves against the effect, or if the effect on it ends, the target is immune to this fiend's Charm for the next 24 hours.

The fiend can have only one target charmed at a time. If it charms another, the effect on the previous target ends.

Etherealness. The fiend magically enters the Ethereal Plane from the Material Plane, or vice versa.