Thiefless Equipment (3.5e Equipment)
From D&D Wiki
Thiefless Equipment: This effect could be present on any piece of equipment for any body slot.
When an item with this effect is present on a character, all of said character's equipment cannot be unwillingly removed. Items worn cannot be destroyed with the intent of removing the item from the character's person (items can be destroyed normally in combat but cannot be destroyed out of combat with the intent of stealing the equipment or depriving the owner of the items). The owner of the equipment is always subconsciously aware of all "worn" equipment and their effects (though this knowledge only applies after wearing it and does not prevent any effect the item may have).
The owner of the equipment can still remove the equipment themselves. This includes removing the equipment under the influence of mind-control spells. Non-magically controlled influence (bluff, diplomacy, etc.) however, will fail if the subconscious awareness of the worn equipment goes against the influence (i.e. a bluff that the character's armor will kill them if they continue to wear it vs. the awareness that it will not).
Note that this does not include things like money pouches or other items that are not explicitly equipment (i.e. armor, weapons, body slot items, etc.). Also, weapons or other items that are wielded can still be disarmed, but non-wielded items cannot.
Weak conjuration;CL 15th; Craft Wondrous Item; Hardening, grease; Activation: Always active; Weight: Varies lb.; Market Price: 18,600 gp