Amulet of contingency:

• When you are reduced to critical HP, it auto-uses itself and crumbles to dust, and teleports or warps you away to get away from whatever threat you are facing.
• Teleportation makes a bit more flavor sense, but warping allows it to be effective even on non-teleport levels.
• The destination could be the up stairs, but that could be abused on the ascension run. If the amulet is uncommon enough, this could be OK and using them to get through a few levels could be a viable tactic. Otherwise, they could send you to a random destination, or a random destination from among the set of places with no imminently threatening monsters.
• If you die without passing through critical HP range (i.e. any non-HP death, or getting hit with a very powerful attack) it does not trigger.
• Possibly, the amulet slot is the wrong one for such an item because most people would still probably prefer life saving over it. It could possibly be a piece of magical armor, or else be a charged amulet, good for multiple uses.

If a monster is both covetous and has the ability to break boulders, allow them to warp onto the same space as a boulder next to the hero if there is no free space to land, and destroy the boulder with a message like “[Mon] materializes in the same space as the boulder, shattering it to bits!”

When a non-unique warper (and possibly some unique warpers, like non-magical quest nemeses) is cancelled, they cease to be able to warp. This means that levels in Gehennom can contain caged liches that are cancelled and thus incapable of warping out, or of spellcasting for that matter.

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