Right-ho, here goes a first stab at it, based on a mixture of the Ghost and the Shadow, it probably needs a bit of work on the Malevolence:
Lesser Ghost
Medium Undead
Hit Dice: 3d12 (19 hp)
Initiative: +3
Speed: Fly 40 ft. (good) (8 squares)
Armor Class: 17 (+3 Dex, +4 deflection), touch 17, flat-footed 14
Base Attack/Grapple: +1/—
Attack: —
Full Attack: —
Space/Reach: 5 ft./5 ft.
Special Attacks: Malevolence
Special Qualities: Darkvision 60 ft., manifestation, +2 turn resistance, undead traits
Saves: Fort +1, Ref +3, Will +4
Abilities: Str –, Dex 17, Con –, Int 10, Wis 12, Cha 18
Skills: 24?
Feats: 2
Environment: Any
Organization: Solitary, gang (2-5), or mob (6-12)
Challenge Rating: ?
Treasure: None
Alignment: Any
Advancement: 4-9 HD (Medium)
Level Adjustment: —
Malevolence (Su): Once per round, an ethereal ghost can merge its body with a creature on the Material Plane. This ability is similar to a
magic jar spell (caster level 10th), except that it does not require a receptacle. To use this ability, the ghost must be manifested and it must try move into the target's space; moving into the target's space to use the malevolence ability does not provoke attacks of opportunity. The target can resist the attack with a successful Will save (DC 15). A creature that successfully saves is immune to that same ghost's malevolence for 24 hours, and the ghost cannot enter the target's space. If the save fails, the ghost vanishes into the target's body. The save DC is Charisma-based.
Manifestation (Su): A lesser ghost dwells on the Ethereal Plane and, as an ethereal creature, it cannot affect or be affected by anything in the material world. When a lesser ghost manifests, it partly enters the Material Plane and becomes visible but incorporeal on the Material Plane. A manifested ghost can be harmed only by other incorporeal creatures, magic weapons, or spells, with a 50% chance to ignore any damage from a corporeal source. A manifested ghost can pass through solid objects at will, and its own attacks pass through armor. A manifested ghost always moves silently. A manifested ghost can strike with a touch attack or with a ghost touch weapon. A manifested ghost remains partially on the Ethereal Plane, where is it not incorporeal. A manifested ghost can be attacked by opponents on either the Material Plane or the Ethereal Plane. The ghost's incorporeality helps protect it from foes on the Material Plane, but not from foes on the Ethereal Plane.
A lesser ghost has two home planes, the Material Plane and the Ethereal Plane. It is not considered extraplanar when on either of these planes.
