Amulet of protect inventory: negates any erosion, destruction, disintegration, or theft of your items, but every time it does, you take damage.

Solve the problem of pets wasting their hard-trained apport by picking up and dropping objects randomly all over the dungeon, by triggering them only to use it when the hero plays any instrument (or maybe any non-magical instrument). Bonus points if the player can train the pet by playing an arbitrary sequence of notes (chosen by the player) on tonal instruments.

A monster, probably in the y or e class, with an attack that steals an item (or a few items, excluding equipped gear) from your inventory and randomly teleports it somewhere on the same level. This makes object detection and detect treasure nice to use even after a level is fully explored.

Greased items should be immune to getting stolen out of the inventory (except perhaps if it’s a greased armor piece and the stealer is a nymph that charmed you into taking it off).

When a nymph steals an armor item, she remains frozen for as long as it takes you to remove it, thereby preventing her from stealing all your other things while you are removing it.

Some monsters, when dealing what otherwise would have been a killing blow, instead leave you at 1 HP, strip you of some or all of your possessions, and possibly vanish/teleport. Shopkeepers in particular may decide to do this (but some may still decide to kill you).

Bearded axes can be used to strip enemies of other things besides their wielded weapons, such as wands and other utility items.

“Unstealable” object property, which makes an item with that property incapable of being stolen.

Any quest-artifact-stealing attack has to pass an additional roll to work successfully if you currently have the artifact equipped.

If you are polymorphed into a nymph and are lawful, you suffer an alignment penalty for stealing items from other monsters.

If a gold golem is hit by a gold-stealing attack, some gold pieces are put into the attacker’s inventory and the golem loses some of its maximum HP.

In order to prevent nymphs stealing your entire inventory while you disrobe, make their charm-steal attack not steal anything if you are immobilized due to taking off armor. Or make their armor-removal immediate like a foocubus, or give you a chance per turn to resist the charm, based on a Wisdom save.

Leprechauns have a tiny chance, less than 1%, of dropping a credit card on death (or generating with one). Such a card will always be a “Yendorian Express - Gold Card” or “Shamrock Card” when read. They also are capable of stealing any credit card that says either of these things.

Track the amount of Luck increase you have had from a unicorn. If you steal gems from such a unicorn or kill a unicorn you have gotten Luck from, immediately revert that Luck increase.

If someone steals the Amulet of Yendor and ascends on your altar, your god either still grants you immortality or at least an exalted position because after all, you did all the legwork getting it onto Astral.

Magpies, a bird that has a stealing attack; unlike monkeys, the stealing attack is limited to shiny objects (possibly based on their material) that are under a certain weight. Under that rule, rings, gems, and amulets are common targets of theirs. They probably have a rather fast speed, too. They should likely generate in small groups.

Magpies would have an alignment of 0 and lack the M2_HOSTILE flag, and thus may be peaceful to neutrals, but angering one makes all other magpies angry as well.

A monster that, similar to leprechauns, steals items made out of silver, and only items made out of silver.

Define Angels to have an additional amulet-stealing claw attack. If you aren’t carrying the Amulet when they hit you, this attack is skipped. (Actually, perhaps all Amulet-stealing attacks should work this way, where they don’t happen if you have nothing to steal).

Nymph race very similar to dNetHack’s yuki-onna, but based on regular NetHack nymphs (so no association with cold and no iron weapons). Has the same unarmed-attack-automatic-stealing ability that yuki-onna have, and has infinite carry capacity, but low HP.

When you are polymorphed into a monster with a stealing attack, you shouldn’t be able to make a normal attack and also steal something at the same time. Perhaps the stealing attack should only be made when you are barehanded, though this could interfere with martial arts.

Wearing an oilskin cloak prevents theft attacks by nymphs, monkeys and leprechauns.

Stealing gloves (also possibly named “rogues gloves” or “gauntlets of thievery”). 0 base AC, and Rogues begin the game wearing a pair. When you hit a monster barehanded while wearing them, you deal no damage (and don’t train bare handed combat skill) but you get a Dex-versus-monster-AC chance of stealing a random non-equipped item or some gold out of their inventory. You can also attack a peaceful monster with them to attempt to steal something; in addition to the Dex-vs-AC roll, this requires passing both another Dex check and a Cha check for them not to notice. If the Dex check fails, you don’t steal anything successfully; if the Cha check fails, they notice (waking up if asleep) and get mad. If the stolen item is currently equipped, there’s no Cha check; the monster just gets alerted and angry.

Assuming an implementation in which player monsters can steal the Amulet of Yendor from you: they may instead steal an imitation amulet you are carrying in main inventory.

Up for debate whether they should have, say, a fixed 50% chance of stealing the real Amulet regardless of how many fakes you are carrying, or whether they should pick one of your apparent Amulets at random, which would give an advantage to carting around more fakes.

Give Croesus a gold-stealing attack in addition to the regular attacks he has now.

Fire/flame nymph, n, which normally only spawn in Gehennom (or possibly near lava not in Gehennom) and are noticeably stronger than other nymphs. Have two steal attacks which burn any items stolen, and also a fire attack. Potentially a passive fire attack as well. They also explode into fire when killed.

Arch-foocubi which do the same seduction as regular foocubi, but the random number they choose has a higher average than a foocubus’ 1-35, so the chance of a bad effect is greater and it’s less effective to boost your own stats. Perhaps rnd(35) + 25. They are also more grabby than regular foocubi, and will steal jewelry if you have insufficient gold.

Some sort of late-game nymph monster that steals items. Helps mitigate an underlying issue: some of the early-game threats like stealing are completely absent in the late game, with no particular reason for that being the case.

Instead of the Wizard of Yendor stealing all quest artifacts, he can only steal ones that don’t belong to your role, since you didn’t actually earn them.

General artifact-stealing attack; like the Wizard’s quest-artifact-steal attack but applicable to all artifacts and without Amulet of Yendor theft baked in. Archeologist player monsters might use this (“That belongs in a museum!”).

The Master Key of Thievery can be wielded and makes 3-4 stealing attempts per hit. Alternatively, it can be wielded in the offhand while twoweaponing and make 1-2 stealing attempts per hit.

Message for when a nymph finishes stealing something from you: “The [nymph] giggles and vanishes.”

Am amulet versus thievery, which protects you from all theft attacks including nymphs, leprechauns, foocubi, and possibly even Amulet-stealing attacks.

Leprechauns (or anything with AD_SGLD) should steal items made of gold out of the hero’s inventory.

In shops, picking up an item spawns a peaceful monster that vanishes once you pay for the item properly. If you make any attempt to steal, it turns hostile. (The general principle: the more you want to steal, the harder it is to do so.)

Rogues have a 20% (or 10%, or whatever is balanced) chance of stealing a random lightweight item (say, less than 5 aum, or less than 20 aum to include potions) out of a monster’s inventory with every successful melee hit they make. This chance is increased if they are hitting with no wielded weapon or have no secondary weapon or shield, and maybe should scale with experience level too.

The Master of Thieves has a stealing attack that allows him to choose intelligently what to steal.