Armor that becomes cursed should have its enchantment effectively reversed; e.g. a piece of armor will still be +3 but it will make armor class worse by 3 points instead of better. If the armor is negatively enchanted, it still makes armor class worse by that amount.

Leprechaun race: gets unlimited gold-stealing attacks that allow you to teleport each time you steal gold from a monster’s inventory or beneath their feet, which allows you to set up teleportations in advance by luring a monster onto a pile of gold pieces. However, it has weak attribute maximums.

If you enter a room containing open pits of lava, print a message “It is hot in here.” If hallucinating, follow this up with “…but it’s a dry heat!”

A monster (imagined exclusively as a pet) that acts like your shadow in lit places, always being right next to you and possibly dying if it can’t be next to you, but if you’re in a dark area it is free to wander off.

Elves can read the runes on any elvish weapons (and probably also the runed wand). This doesn’t have to say anything important, it could just describe the item.

Nazgul can innately see invisible.