+X weapon into -X weapon when others use it?

[Yogibear41]

Is there anyway to make say a +5 sword turn into a -5 sword when used by someone other than the intended user? Or other similar effects that cause magic items to become hindrances to people who may steal them and/or try to use your own magic items against you?

[MisterKaws]

You can make self-only enhancements, place restrictions(but UMD), curse them to be unremovable(can't steal), add any of the various "summon" effects on them, or some other stuff, but I've never seen an enhancement that does what you want.

I suppose you could make a -x cursed item and then add a self-only enhancement at +2x to nullify the curse, but it would get real expensive real quick, so I don't think that's viable. Overall, it's easier to just make them unable to steal it in the first place.

[Venger]

You can make self-only enhancements, place restrictions(but UMD), curse them to be unremovable(can't steal), add any of the various "summon" effects on them, or some other stuff, but I've never seen an enhancement that does what you want.

I suppose you could make a -x cursed item and then add a self-only enhancement at +2x to nullify the curse, but it would get real expensive real quick, so I don't think that's viable. Overall, it's easier to just make them unable to steal it in the first place.

yeah, that specifically is probably more trouble than it's worth.

if you fight a lot of disarmers or the like, you could always drop 1kgp on a lesser weapon crystal of return. pulls the thing to your hand as long as it's within 30 feet as a move. plus you can draw it as a free action, which is always nice.

[Zanos]

The item creation rituals in DMGII allow characters to create magic items that only work for the creator. Won't be a hindrance, but anyone who snags your sweet loot is stuck with mundane rings, masterwork swords, and a warm but otherwise unimpressive cloak.

[Mordaedil]

Is there anyway to make say a +5 sword turn into a -5 sword when used by someone other than the intended user? Or other similar effects that cause magic items to become hindrances to people who may steal them and/or try to use your own magic items against you?

Yeah, it's called a Holy Avenger.

Joking aside, you don't have to go as far as to make it a penalizing weapon; merely giving it the properties of a bane weapon when wielded by the proper user and mundane in the hands of others is enough. Perhaps being wielded by others triggers the vicious property, which deals damage to its wielder as they deal damage to their opponents. That's technically what the Holy Avenger is, anyway, a +2 cold iron sword given the bane property in the hands of a paladin, plus extra.

Using that idea as a template, go wild.

[DedWards]

Going by Pathfinder rules (I'm not sure the ruling in any other system), the Holy enchantment gives a negative level to any Evil aligned character that attempts to wield it. The same is true for a Good aligned character using a weapon with the Unholy enchantment. Not exactly what you want, but is only a +2 enchantment, so not too expensive.

[icefractal]

It's not quite the same, but the Masterslaying ability (BoVD) will make anyone who tries to use your weapon against you regret it. At the command of the one wearing the scabbard / belt hook (you, hopefully), it attacks whoever is wielding it.