|The AD&D ghost|
"I detect a foul evil emanating from the crypt", said the paladin during last game session. "Well, we're here to kill vampires", was the general group consensus - let's pop that sucker open and get the stakes and garlic ready. "This feels worse than usual, if that's possible… something more malign than a vampire". Nonetheless, they pressed forward, breaching the crypt, and encountered their first GHOST.
Considering how common they are in real world folklore, ghosts are not very common in D&D; after long careers of playing AD&D and 3E, none of my players could recall encountering a ghost. I couldn't recall ever running one in an encounter. I had some vague concerns how the group would beat the ghost based on its peculiar abilities, but I let her rip anyway; players are resourceful and my group frequently surprises me.
You see, ghosts are ethereal, and can only be damaged by ethereal combatants. Oh - and telepathy. Ghosts are also effected by telepathy. So how many different ways can your group current group engage in ethereal and/or telepathic combat? (If you're like us, the answer is none).
I can think of two magic items that allow someone to drift into the ethereal plane - the lame "oil of etherealness" and the even lamer "armor of etherealness". A few rare psionics disciplines allow ethereal travel and telepathic combat - except we don't use them.
Meanwhile, the ethereal ghost can magic jar with impunity, seizing control of a player character and using the possessed body to beat on his compatriots.
My players did their best, busting out their Potion of Undead Control (the ghost saved against the charm effect) and failing in their Turn Undead attempt. After those failures, they Webbed their possessed companion, and when the ghost gave up the possession, they ended up cutting him free and running for it.
Castle Ravenloft has a library stocked with books on the nature of the undead, so they raided the library before the end of the night to come back at the problem with some fresh tactics after researching ghostly vulnerabilities.
After the session, I started thinking through how difficult is a ghost encounter, and started considering all the different ways they could destroy one without ethereal travel; Destroy Evil or Raise Dead (in BX/Labyrinth Lord) are the most straightforward, but both are 5th level spells. I poured over the game text a little more to see if I should put in a folkloric element - destroying a fetter that ties it to the mortal world, or somehow driving it from the material plane (maybe via the 4th level Exorcism). And then I noticed a key sentence - this is straight from the AD&D 1E monster manual:
Ghosts attack by two means: Any creature within 6" of one is subject to attack by magic jar spell from the ghost. Unless the ghost becomes semi-material to attack by other means, it can otherwise only be combated by another in the ethereal plane (in which case the ghost has an armor class of 8) or by telepathic means. If the ghost fails to magic jar its chosen victim, it will then semi-materialize in order to attach by touch (in which case the ghost is armor class 0).
Aha! The text implies the ghost picks a single victim to magic jar, and if it fails to capture them, it will materialize and continue to attack on the physical plane. Semi-materialized ghosts can be swatted with magic weapons. That's a pretty important implication - it saves the ghost from being an invulnerable road block.
The whole reason I got into a jam is because we're not actually playing AD&D 1E, we're using Labyrinth Lord's Advanced Edition Companion, and the subtle language about a single target didn't make it into the text; the AEC implies the ghost's primary and usual attack is the Magic Jar; materialization is purely optional (and suboptimal). So I'm putting out a cautionary note about the importance of cross-checking subtle language when it's imported into a retro-clone; clone authors are tossing the text to avoid infringement, and sometimes that original phrasing was important.
I do have a follow-on question for any D&D lore masters, however: Does the Protection from Evil spell protect an individual from Magic Jar in OD&D or 1E? I know it works that way in later editions (it's in the SRD, for instance), but I don't recall when it entered D&D - I was looking for a reference in AD&D 1E and couldn't find one. I'm wondering if that entered via 2E AD&D or perhaps Dragon?