Cancelled, non-unique warpers (and possibly some unique warpers, like non-magical quest nemeses) shuts down their warping. This means that cages in Gehennom can contain liches that are cancelled and thus incapable of warping out.

Make it possible to define a “retreat point”, or a set of retreat points, for a warping boss monster. They will warp to that point to retreat, rather than always picking the upstairs. Possibly, if they have multiple retreat points, they will only ever use the first one they randomly select.

Remove covetous warping entirely. However, a change like this would need to take into account that it makes the vast majority of boss fights a lot easier and more boring in that they would tend to consist just of the hero and boss standing next to each other hitting each other until the boss dies, so it would need to come with some improvements to boss fights, such as more interesting tactical AI where they will disengage momentarily and multiple forms (i.e. you “kill” it and then it becomes stronger before finally being defeated).

Change covetous warping so it only works for demon lords on their lair levels, and then they can only warp back into their lair.

Covetous warpers can only warp to the location of the item they covet. This means that if you are carrying it, they can warp to you all they want, but they can’t warp back and forth to the stairs.

Covetous monsters can warp to the up stairs only if they know where the up stairs are. Demon lords would know this in their own lairs, but not otherwise, and monsters randomly spawned on a level may or may not.

Covetous warping only works on teleportable levels. It should also count as a regular teleport and cost Pw for the warping monster.