Captain Ghost

Ethereal Sight. The ghost can see 60 feet into the Ethereal Plane when it is on the Material Plane, and vice versa.

Incorporeal Movement. The ghost can move through other creatures and objects as if they were difficult terrain. It takes 5 (1d10) force damage if it ends its turn inside an object.

Multiattack. The captain makes three melee attacks: two with its scimitar and one with its dagger. Or the captain makes two ranged attacks with its daggers.

Scimitar. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 6 (1d6 + 3) slashing damage (1d6) necrotic damage.

Dagger. Melee or Ranged Weapon Attack: +6 to hit, reach 5 ft. or range 20/60 ft., one target. Hit: 5 (1d4 + 3) piercing damage  (1d6) necrotic damage

Withering Touch. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 17 (4d6 + 3) necrotic damage.

Etherealness. The ghost enters the Ethereal Plane from the Material Plane, or vice versa. It is visible on the Material Plane while it is in the Border Ethereal, and vice versa, yet it can't affect or be affected by anything on the other plane.

Horrifying Visage. Each non-undead creature within 60 feet of the ghost that can see it must succeed on a DC 15 Wisdom saving throw or be frightened for 1 minute. If the save fails by 5 or more, the target also ages 1d4 × 10 years. A frightened target can repeat the saving throw at the end of each of its turns, ending the frightened condition on itself on a success. If a target's saving throw is successful or the effect ends for it, the target is immune to this ghost's Horrifying Visage for the next 24 hours. The aging effect can be reversed with a greater restoration spell, but only within 24 hours of it occurring.

Parry. The captain adds 2 to its AC against one melee attack that would hit it. To do so, the captain must see the attacker and be wielding a melee weapon.