While playing a dungeon with gbhosts, one of my players put up a good question. Can ghosts possess items? And if so, do they make the item stronger? I know ghosts are "attached" to certain people or places, which keeps them in the material plane, but could they be "attached" to a certian item? Also, one of my players is a cleric who "worships" his ancesstors. Could he then call upon one of his friendly ancestor spirits to inhabate his armor/weapon and make it stronger? All sugestions are welcome.
Ghosts in pathfinder do not possess items, possibly some undead that are very similar do, they are restless spirits that come into being because they have unfinished business it is not a creature that should come on back from the dead on request. In previous sources items are more often inhabited by demons or other (non-undead) spirits.
Often intelligent items have intelligence and a personality that mirrors their creator or a previous wielder, in most cases this is not the actual creature's spirit but an artificial intelligence, maybe a soulfragment or impression left behind in a material shell.
In short ghosts should not be in players control, they should have a detailed background and a means to be laid to rest.. they possibly might be attached to an item but they do not inhabit such an item.
From a game mechanics point of view if your player wants to make his weapons / armor stronger by allowing it to inhabit by ancestor spirits, I advise to use the craft feats and add this to the flavor description rather than change the effect of the feat.
By the RAW, there is no way for an item to be possessed by a ghost. However, I would allow it, based on flavor. I would not change any mechanics nor allow any benefits from this.
I seem to recall a 3.5 PrC or base class that could call upon their ancestors (or other spirits) for short term benefits. Any help out there on locating this class, please?