Non-corporeal. While in the ethereal state, an incorporeal creature cannot attack material creatures. Likewise, corporeal creatures cannot affect a non-corporeal creature unless they enter the Ethereal Plane. This means creatures on the Material Plane cannot attack or otherwise affect a non-corporeal creature using weapons, spells, items, or abilities unless these are noted to have a special power enabling them to affect ethereal or non-corporeal creatures. Ghosts can be seen by those on the Material Plane (unlike normal ethereal creatures) but can move in complete silence if they wish. In the ethereal state, a creature can pass through solid objects—sideways, upwards, or downwards. Non-corporeal creatures are unaffected by cure wounds, heal, or resurrect/raise dead spells. They are also immune to polymorph. In order for a ghost to touch a creature, it must become semi-material using it's phasing ability.
Phasing. (minor, 1 segment) A ghost can partially phase in or out of the Material Plane as a minor action (only one such phasing action is allowable each round). It will become "semi-material" in order to touch an opponent or fully ethereal to avoid attacks.
Supernatural Horror. The supernatural power of a ghost is such that the mere sight of one causes any humanoid being to age 10 years and flee in panic for 2d6 turns unless a Wisdom (fear) save vs. Spell is made (a save negates both effects). Note that magical ageing such as this will require a Constitution save vs. System Shock (or the creature will die). Clerics above 6th level are immune to this effect, and all other humanoids above 8th level add +2 to their saving throws.
Touch Attack. (major, 1 segment) A semi-material ghost attacks by reaching through any protective coverings and touching a creature. Opponents are considered AC 10 unless they use magic or Dexterity. For example, a fighter wearing +2 chain mail, with a +1 shield, wearing a ring of protection +1 and has a Dexterity of 16 will be AC 4 against a ghost's attack (10 - 2 - 1 - 1 - 2 = 4). If the attack hits, the victim ages 10-40 years (1d4 x 10). Note that magical ageing such as this will require a Constitution save vs. System Shock (or the creature will die).
Undead Traits. Undead are immune to the following spells or effects: ageing, charm, command, ESP, fear, hypnotism, paralyzation, poison, scare, sleep, and suggestion. All aligned undead radiate evil that may be detected (the degree of which is normally a function of their hit dice, although there are exceptions).