The Amulet of Yendor (and fakes) should have some bright, noticeable color that is not the same as the metal color used by every other amulet type.

In variants where a monster can grab the Amulet on Astral and attempt to ascend with it: they gain the ability to shove monsters out of their way while pathfinding towards their high altar, but they are grudged by all monsters who are crossaligned with them.

To nerf the strategy of dropping the Amulet to cast spells, but not to the point of UnNetHack’s teleporting it anywhere on the level, it teleports randomly within a fixed radius every time it’s dropped. (Possibly on the Astral Plane it always teleports away from the nearest high altar, so you can’t use it to jump ahead.)

The Amulet drains your power when you cast spells, even if you’re not carrying it, if it’s on the ground nearby. The amount of power drained is proportional to your closeness to it.

You have a boosted chance in getting crowned if you are carrying the Amulet of Yendor. This possibly also nullifies the downsides of crowning, such as an extended prayer timeout.

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.

If Astral denizens are able to steal the Amulet from you and try to ascend with it: The amulet-bearer uses a special AI algorithm which pathfinds towards their high altar, using a shortest-path algorithm that avoids monsters if possible but if none are available will plot a path that goes through the minimum amount of monsters. They will only attack when the next square on their path is occupied by a monster, and they will only attack that monster.

If Astral denizens are able to steal the Amulet from you and try to ascend with it: Keep track of the god of the current amulet-bearer (whether you or someone else). Priests and angels aligned to that god grudge all others, and all others grudge them.

Wishing for the Amulet of Yendor doesn’t fail and give you a fake if you have ever held it in the past. In that case, a wish for it will reclaim it from wherever it was. The monster who was currently holding it may appear, too, however.

If someone of a different god steals the Amulet from you on the Astral Plane and sacrifices it to their god, your god will hit you with a wide-angle disintegration beam in frustration that you got so close and then blew it.

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).

Assuming an implementation in which Gehennom starts to get destroyed after you remove the Amulet: When you kill the high priest of Moloch, he gives you a multiline death message calling you a fool and saying you don’t know what you have done, and maybe hinting a little bit at why Hell is about to go to hell.

When you first pick up the Amulet of Yendor, you get another screen-overwriting message similar to what happens in the quest and at the beginning of the game, directing you to travel back up the dungeon and give it to your god.

When you kill the high priest of Moloch, Moloch himself shows up with the Amulet, and you have to beat him up and take it from him.

When the Wizard of Yendor has the real Amulet, he gets an infinite mana pool to cast from, or otherwise his magic becomes more powerful.

You can only use cursed potions of gain level once or twice while carrying the Amulet. After a few uses, the Amulet will start to pull you back down as you rise up, wasting the potion.

Invoking the Amulet of Yendor gives you a random possibly helpful, possibly harmful effect:

• Temporary intrinsic regeneration.
• Recover 5d10 Pw for free.
• Paralyze all adjacent monsters for several turns.
• Paralyze you for several turns, bypassing free action.
• Teleport.
• Shuffle blesses and curses on your inventory items.

You can invoke the Amulet on Moloch’s high altar to destroy it; this does something good later for you (more points? prestige?) but Moloch will now harrow and hound you down all the way back through Gehennom even more fiercely than usually.

The Amulet of Yendor blocks teleporting within a dungeon level, but only after a certain radius. Short-range teleports work fine.

Various alternate endings for the game:

• You can take over an abandoned shop, stock it with items and mimics, and settle down as a new shopkeeper, ending the game. This creates a bones file with you replaced by a shopkeeper bearing your name.
• You can eradicate the Wizard of Yendor from the game entirely and forever, becoming the next Wizard of Yendor yourself. This is done by standing in the center of the Wizard’s Tower wearing the Amulet of Yendor and invoking it. This respawns a beefed-up Wizard; defeat him and the game ends with you as the next Wizard. (It’s missing an end condition for what happens if you escape the dungeon while in this semi-powered-up state.)
• You can claim the Amulet’s power for yourself rather than giving it to a god. While anywhere on Astral, invoke the Amulet while wearing it. You get some big and unspecified surge of power from it. Furious at your betrayal, your god smites you every way they can, joined in by the other gods and the Riders, calling to bear all their priests, angels and Archons, which spawn in swarms on the high altars. (You also lose sanctuary.) You have to reach each high altar and shut it down/destroy it. Once you have done this, you win and keep the Amulet’s power for yourself, as long as you can manage to hold on to it.
• Alternatively, there is another way to do the “claim the Amulet for yourself” way: once you invoke the Amulet, a timer starts. The gods have only this much time to kill you or take the Amulet away before you become invincible to them. Would require some anti-boulderforting measures though. Or, you have to escape the Astral Plane back to the surface wiht all the gods trying to impede your progress.
• You want to break the power of the Amulet so no one gets it, and break the gods’ dominion over the world. You must invoke the Amulet while standing on each high altar to destroy it. (Not mutually exclusive with the other ending: you don’t channel the Amulet’s power into yourself, but into the high altar. In a game with both endings, you trigger the other one by invoking it anywhere except a high altar.)

Also see the Astral Escape Patch.

If you used to have the Amulet but now don’t for some reason, your death message gets “(without the Amulet)” appended to it.

More harassment effects: the chance of respawning the Wizard is a fixed 1/7 and the rest of the effects are equal probability. Multiple non-duplicate effects may happen at the same time.

• Unchanged: curse items, summon nasties, vaguely nervous, aggravate monsters
• Darken much of the level, and extinguish, destroy, or cut the remaining lifetime of light sources. Maybe also blind the player.
• Drop boulders around the upstairs, or iron bars.
• Spawn pools centered on the player, with sea monsters in them.
• Spawn lava around the level, not under the player.
• Create a hole or pit under the player.
• Create a stinking cloud centered on the player.
• If you are carrying the Amulet, it teleports to a random square on your level or the level below.
• If you are carrying the Amulet, it (and possibly any fake Amulets) becomes heavier. This either lasts until the next harassment triggers, or is permanent but the total amount of weight added to the amulet has some sort of cap on it. This is interesting primarily because it targets carry cap, which is a valuable end-game resource.
• A variety of powerful player debuffs such as dealing half damage, taking double damage, blocking HP or Pw regeneration, super hunger, etc.

Restore the Amulet Delivery Service to the game: demon lords in the Sanctum, but not the Wizard, will fight the current holder of the Amulet of Yendor for it. Only do this if lugging a demon lord down to the Sanctum is considerably harder than just fighting through the Sanctum is itself, and no demon lord is actually guaranteed to win against the High Priest.

Player monsters, crossaligned priests, and hostile angels on the Astral Plane are able to steal the Amulet from you. Should they get it, they will try to make a beeline to their high altar to sacrifice it. The player is also able to steal the Amulet back, though; and wearing the Amulet acts as one turn of protection against it being stolen; an attempt to steal it will just remove it from your neck. If something else ascends, your game ends in an escape. However, all these monsters are hostile towards the Amulet-bearer, not you; so if it gets stolen from you, the pressure will let up a bit.

You can invoke the Amulet of Yendor exactly once for a wish, with some unspecified major drawbacks.