Invisible items are a game mechanic that appears in SLASH'EM, GruntHack and SlashTHEM. Some items may be generated or turned invisible; these items on the ground cannot be seen without walking over them, unless you have the see invisible property. Invisible items are mostly the same in function as normal items with additional quirks due to their invisibility - and exceptions depending on the item.
There is a 1⁄1250 chance that a randomly generated item will be created invisible, with the exception of mummy wrappings, zorkmids and boulders in Sokoban. Potions of see invisible can still be made invisible. The wand of wishing in the Castle will always be generated as invisible inside its container.
If an invisible monster is killed and leaves a corpse, the corpse will be created invisible. Zapping an object with a wand of make invisible or dipping it in a potion of invisibility will turn it invisible.
Invisible items are rarely encountered and generally have no appreciable difference from their visible counterparts, e.g. an invisible blindfold or towel will still blind you as normal. There are some exceptions, however:
- An invisible weapon has a +3 to-hit bonus against monsters that cannot see invisible. The disarm technique cannot be used against invisible weapons.
- Invisible items cannot be stolen by a monster that cannot see invisible, with the exception of an invisible set of body armor or cloak worn on top of a visible t-shirt or body armor; currently, no monster with a theft attack in SLASH'EM can also see invisible.
- Monsters will not pick up invisible objects if they cannot see invisible, but this does not prevent them from pathing to the item. The end result is that they will constantly stand on top of the item as if trying to pick it up, but cannot.
- Invisible items such as scrolls and books cannot be read unless you can see invisible. Monsters do not have this same restriction, but cannot pick up invisible items without see invisible anyway; as such, this only becomes important if a monster is randomly generated with an invisible item. An invisible mirror will not function if the affected cannot see the item.
- In GruntHack, slightly different descriptors are used for the gradual rotting of an invisible corpse (e.g. "smelly" instead of "off-color"); this is typically seen with stalker corpses in particular.
Walking over an invisible item will give the same message as walking over other unseen items (e.g., while blind). However, invisible corpses that petrify on contact such as a cockatrice will not stone you if you are not wearing gloves.
- You feel here <foo>.
- You walked over a square with one or more invisible items.
- Where did the <foo> go?
- You dipped a visible item into a potion of invisibility.
- So that's where the <foo> went!
- You dipped an invisible item into a potion of see invisible.