A headless race, “Akephalos/oi”, which has no head and its face on its chest, so it is incapable of wearing helms, and is blinded (and cannot drink potions) if a shirt or body armor is worn.

Also a dullahan/cephalophore race which Knights can play as. They are also headless and cannot wear helms, but they carry their head as an item and can place/throw it elsewhere. Vision is based on where the head is, so it is possible to leave the head somewhere and have the body moving around blindly in a different area of the map.

Artifact ring of warning that, in addition to providing warning, has some of the properties from UnNetHack’s Clarent. When worn, it shows all pets on the level, wherever they are, and can be invoked to increase tameness of all pets in line of sight.

Magic collar, an amulet without a randomized appearance, which you can apply to a pet to make it wear it, assuming it has a neck. The pet then becomes visible to you at all times while it’s on your level (similar to seeing it with telepathy) and possibly tracked in #overview if it’s not on your level. Farlooking a pet wearing a magic collar shows HP and other additional information as if you had used a stethoscope on it.

Not specified what effects there would be, if any, if the player wears the magic collar.

A cursed potion of enlightenment grants you temporary darkvision.

When a monster and a gas cloud are on the same space, and you are adjacent to that space and non-blind, the game should render the monster rather than the cloud.

Option to configure your character to be nearsighted, which prevents you from seeing things more than a few spaces away from you unless you’re wearing lenses. You can also be farsighted, which means you can’t read scrolls or spellbook unless you’re wearing lenses.

If you are not deaf, non-stealthy monsters that you can’t see (because they’re out of sight or invisible) occasionally show up as an I when they move. Blindness has no effect, except indirectly that adjacent spaces also count as out of sight.

If you can see a monster only with telepathy, you cannot see its peaceful/hostile status, so all monsters appear hostile by default (except tame monsters, which you can still see as tame). Likewise, you can’t see the monster names of non-tame monsters you can see only with telepathy.

When blind and holding a leash with a pet on it, you can see the pet.

Magic portals are never hidden.

If there are items on a pit space, the vision code doesn’t render them until you’re adjacent to the pit, at which point the pit is automatically mapped and you see the items. If there are no items in the pit, it remains undetected.

Fog clouds block line of sight.

Monsters that are MZ_HUGE or larger block line-of-sight like the giant turtle does in dNetHack.

A level 5 or 6 divination spell that creates a tame speed 0 monster. This new sort of monster gives you permanent vision in a radius around it if it is tame.

In certain cases, you can see what telepathic monsters can see in a radius of 2 or 3 centered on the monster, assuming it fails a saving throw versus you reading its mind.

If you apply a mirror at an empty square and that square is a “corner” (in a corridor), you gain temporary vision in the perpendicular line around that corner. If it’s a T-junction you look both ways. There is a “Done.” at the end like detect monsters has.

Elves get low-light vision, which doubles the radius of light sources, rather than infravision. It also gives them vision on dark squares that are orthogonally or diagonally adjacent to a lit square.

Statues block line of sight.