A covetous monster is one who desires one or more unique items or quest artifacts. Covetous monsters have a distinctive movement pattern which involves constantly warping to and from the up staircase (or to the down staircase while in upward-progressing branches), and they will attack any monster carrying an item they covet (except for the high priest of Moloch and the Wizard of Yendor). Covetous monsters will pick their desired items up off the ground, whether it is you or a dying monster that drops them.
Some covetous monsters also possess an attack which enables them to steal coveted items from your inventory. Quest artifacts can be protected by stashing them in a container. There is no defense against this theft for items in your main inventory; this is especially troublesome if your only source of magic resistance is your quest artifact, and it means that the unique items will always be vulnerable, since they cannot be stashed.
The following items are coveted by various monsters:
|Your quest artifact||All quest nemeses, Wizard of Yendor|
|Other roles' quest artifacts||Wizard of Yendor|
|Bell of Opening||Wizard of Yendor|
|Candelabrum of Invocation||Vlad the Impaler, Wizard of Yendor|
|Book of the Dead||Orcus, master liches, arch-liches, Wizard of Yendor|
|Amulet of Yendor||Asmodeus, Baalzebub, Demogorgon, Dispater, Geryon, Juiblex, Orcus, Wizard of Yendor, Yeenoghu|
Only quest nemeses and the Wizard of Yendor have stealing attacks. On one-twentieth of the hits from such an attack, the monster will look for one of the above items in your inventory; if they find one, they will steal it and, if capable, teleport away.
The Wizard of Yendor is most notorious for this; if he casts Double Trouble, his double has a chance of carrying a cheap plastic imitation of the Amulet of Yendor, which can be confused with the real Amulet if it is stolen.
Covetous monsters behave quite differently from lesser denizens of the dungeon, owing both to their generally powerful natures and their insatiable desires for their respective items.
When a covetous monster wants to attack, they simply appear adjacent to you, or as close as they can get if there is no open space next to you. This type of teleportation (often informally described as "warping") is not prevented on non-teleport levels.
A damaged covetous monster will warp to the up stairs to heal. The damage does not need to be critical; even a few HP lost will send them fleeing. If the covetous monster is in an upward-progressing branch (Sokoban, Vlad's Tower, or the Wizard's Tower), they will instead teleport to the staircase or ladder down. While healing, the monster may occasionally appear for a quick attack or two before returning to the stairs. They will not resume a sustained assault until fully healed.
If a covetous monster succeeds in stealing one of your items, they will teleport away. This is not a warp, but a standard teleport which can be blocked by a non-teleport level or the teleport suppression effect of the Amulet of Yendor. Even if the monster successfully teleports, they will usually warp right back to you to continue their assault.
If you pursue a covetous monster to the up stairs, they will escape to the level above. When you follow, they will immediately warp to the new up stairs to continue healing. You may end up chasing them all the way to dungeon level 1. From there, if they aren't carrying any unique items or quest artifacts, they can escape the dungeon entirely.
Covetous monsters ignore Elbereth when warping to the up stairs. They follow the normal rules for respecting Elbereth in all other situations.
Covetous monsters prioritize obtaining their coveted items over any other task, including attacking the player character. A covetous monster will attack a monster who happens to hold the item they covet. The item-stealing attack itself has no effect in monster-on-monster combat, so the attacker will have to kill their target to get the item. However, covetousness will never induce a monster to attack the high priest of Moloch or the Wizard of Yendor.
Covetous monsters cannot be tamed by any means; however, you can obtain a tamed master or arch-lich by either taming a lower lich and letting it grow up, or polymorph another pet. The Wizard of Yendor and all quest nemeses cannot even be pacified.
While other monsters covet your quest artifact and the invocation items, only the Wizard of Yendor and your quest nemesis can actually steal them. On one out of twenty hits, this attack tries, in order, to steal first any quest artifact, then the Amulet, the Bell of Opening, the Book of the Dead, and finally, the Candelabrum of Invocation. The attack will only ever steal one item, and always tries to steal items in this order, regardless of what items the monster covets. The Rogue quest leader, the Master of Thieves, is also capable of stealing covetable items should he be angered, since he is also the Tourist quest nemesis.
Interestingly, monsters that are not the Wizard can be fooled by "fake" items. That is, if you have both the real Amulet and a fake amulet, or if you have both the Bell of Opening and a normal bell, a monster trying to steal the artifact may in fact steal the fake. Specifically, they will steal whichever item comes first alphabetically in your inventory, so you can arrange for the monster to always steal the fake item this way. This is rarely useful; the Wizard specifically cannot be faked out in such a manner, and the only other monster with an amulet-stealing attack is your quest nemesis. Since your quest nemesis always starts with the Bell of Opening, and you can't get the Amulet until you have it, the opportunity for this situation will almost never arise. The one exception might be those who choose to steal the Bell from their quest nemesis through polyself into a nymph; they might want to carry a normal bell to prevent their quest nemesis from stealing the Bell of Opening back, as unlike the quest artifact, the Bell cannot be bagged.
Because they flee at the slightest scratch, are much more mobile than most players, and are invariably high-level and so have a lot of hit points, covetous monsters can be very frustrating to deal with. The easiest option, if you have teleport control, is to teleport to the up stairs before the monster does. If you have a scroll of scare monster to spare, drop it, and you can safely dispatch the monster when they follow. If not, you have at least cut off their escape route and forced them to fight you to the death.
If you can jump, it is possible to move into a position a knight's move away from the stairway and wait. The covetous monster cannot attack you in melee from the stairs and is less likely to go upstairs, though they can summon nasties. Then, wait until the monster warps next to you and jump at the stairway. Even without jumping, you can stand adjacent to the stairs and wait for the monster to teleport to another adjacent tile off of the stairs, then move onto the stairs to block the monster's escape; but the monster will continue to attack you while you are adjacent.
Teleporting to the stairs is not always an option—you may lack teleport control, be on a non-teleport level, or have the stairs blocked by another monster. If the covetous monster is a follower, you could also flee to the down stairs, head down when the monster is next to you to allow them to follow, and hope you land on the up stairs. Also, it is possible to kill some of the weaker or slower covetous monsters before they can warp back to heal; silver weapons or projectiles with a multishot bonus can work particularly well for this.
Covetous monsters are prevented from teleporting while paralyzed. A reliable method to paralyze a covetous monster is to wield a potion of paralysis and hit them with it while wearing a ring of free action. This should provide enough time to dispose of them while they are paralyzed.
Many covetous monsters are generated meditating. If you wake them while standing on the stairs, they will teleport to you but be blocked from escaping. This is most reliably done by quaffing a cursed potion of invisibility, or by allowing a hostile spellcaster to cast the aggravate monster spell. This method will not affect the Wizard of Yendor from outside his tower.
Covetous monsters are defined by one of the following flags in monst.c: M3_WANTSARTI, M3_WANTSCAND, M3_WANTSBOOK, M3_WANTSAMUL, or M3_COVETOUS.
There is also a M3_WANTSALL flag. It has the same value as M3_COVETOUS, but is not used by any monsters. It seems likely that M3_WANTSALL was intended to indicate monsters that want all of the major items, whereas M3_COVETOUS was intended as a mask to check if a particular monster wants at least one major item. If this is the case, the Wizard of Yendor should be specified as M3_WANTSALL instead of M3_COVETOUS. However, since the two symbols have the same value, this does not actually affect gameplay.
Prior to NetHack 3.6.1, the Wizard of Yendor did not covet the quest artifacts of other roles, only your own. Also, both quest nemeses and the Wizard could not steal quest artifacts of other roles, and prioritized stealing the Amulet before your quest artifact.
A user has suggested improving this page or section as follows:
"Include differences between SLASH'EM and vanilla which apply to engraving Elbereth or using a scroll of scare monster on the upstairs."
It is not uncommon for the Wizard of Yendor to appear in Moloch's Sanctum, and immediately engage the high priest of Moloch for the Amulet. Since neither combatant does much physical damage (the wizard is entirely incapable of dealing damage to monsters), both can heal themselves, and covetous monsters can't steal from other monsters, this is generally a stalemate. The demon princes, however, are mostly quite capable of taking out the high priest.
One exploit of this behavior, often used by speedrunners, is to lure a named demon (usually Asmodeus) into the Sanctum. He will quickly dispatch the high priest, retrieve the Amulet, and then return to attack the hero. The player can thus retrieve the Amulet without moving more than one space from the up stairs.