Ethereal Sight. The ghost can see 10 meters 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.
Spellcasting. The ghost uses Divinity (Cha) to cast spells (spell save DC 13, +5 to hit with spell attacks). It has 8 mana, a mana limit of 2, regains all expended mana when it finishes a long rest and regains half its total mana when it finishes a short rest. It knows the following spells:
Withering Touch. Melee Spell Attack: +5 to hit, reach 1 m. Hit: 14 (4d6) 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 (1/turn). Each non-undead creature within 10 meters of the ghost that can see it must succeed on a DC 13 Will 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 restoration spell augmented to greater restoration, but only within 24 hours of it occurring.
Possession (Recharge 6). One humanoid that the ghost can see within 1 meter of it must succeed on a DC 13 Will saving throw or be possessed by the ghost; the ghost then disappears, and the target is incapacitated and loses control of its body. The ghost now controls the body but doesn’t deprive the target of awareness. The ghost can’t be targeted by any attack, spell, or other effect, except ones that turn undead, and it retains its personality, Intelligence, Wisdom, Charisma, and immunity to being charmed and frightened. It otherwise uses the possessed target’s statistics, but doesn’t gain access to the target’s knowledge, class features, or proficiencies.
The possession lasts until the body drops to 0 health, the ghost ends it on its turn (no action required), or the ghost is turned or forced out by an effect like the dispel evil and good spell. When the possession ends, the ghost reappears in an unoccupied space within 1 meter of the body. The target is immune to this ghost’s Possession for 24 hours after succeeding on the saving throw or after the possession ends.
No concoctions, maneuvers, or spells
All creatures in this system should have maneuvers or spells. You should add some maneuvers or spells to this creature. If you do so, please make a suggestion on github so I can finish adding maneuvers and spells to all creatures via https://github.com/mlenser/kryx-rpg-issues/issues/9