The Ghost of Avernus

Taskmaster Whip. Melee Weapon Attack: +11 to hit, reach 10 ft., one target. Hit: 10 (2d4 + 5) slashing damage plus 33 (6d10) force damage.

Summon Devil (2/Day). You summons an Narzugon as an action. The summoned devil appears in an unoccupied space within 60 feet of the you, acts as an  ally to you, and can't summon other devils. It remains for 10 minutes, until you die, or until you dismisses it as an action.

Ghostly Devil (1/Day). You are a Ghost of Saltmarsh, and have been given the gifts of the small towns mysterious past. As an action you can cast the Etherealness once a day requiring no components or spell slots.