As indicated by the name, the property allows you to see monsters that are invisible. While you possess the property, tame and peaceful monsters that have a means of becoming invisible will apply it: monsters with potions of invisibility will quaff them, monsters that can cast disappear will do so, and monsters with a wand of make invisible will zap it at themselves. This occurs regardless of whether you have the property temporarily or otherwise.
Monsters that can see invisible will not misdirect their attacks towards you or another invisible monster and are not subject to the -2 to-hit penalty against invisible targets, though they can still be affected by any displacement that the target has.
The see invisible property can be acquired through the following methods:
- Drink a potion of see invisible (permanently if blessed, and temporary otherwise).
- Eat a stalker corpse or tin while already invisible; note that this also gives permanent invisibility.
- Be crowned by your god.
- One possible effect of sitting on a throne with positive Luck, if you do not have the property as an intrinsic.
- One possible effect of quaffing from a non-magic fountain.
- Wear a ring of see invisible, or eat the ring (which has a 1⁄3 chance of conveying the intrinsic).
- Be a Monk of any experience level or a Ranger at experience level 15.
- Polymorph into a monster with intrinsic see invisible.
Monsters with see invisible
The following monsters possess see invisible as an intrinsic:
- h mind flayer
- h master mind flayer
- y black light
- A Aleax
- A Angel
- A ki-rin
- A Archon
- all D dragons
- E stalker
- Y sasquatch
- All non-undead elves
- @ high priest
- @ Wizard of Yendor
- @ Croesus
- & marilith
- & ice devil
- & pit fiend
- & balrog
- All demon lords and princes
- The Riders
- Quest monsters
For roles besides the Monk (who starts with the intrinsic), see invisible is fairly trivial to obtain on a permanent basis compared to most properties: quaffing a single blessed potion of see invisible, crowning, or eating stalker meat while invisible will give you the intrinsic permanently, rendering most other sources of the property redundant and easily saving a ring slot. A tin of stalker meat or a blessed potion of see invisible can still be worth carrying around as a backup in case you lose the intrinsic, usually as a result of a gremlin attack.
One negative side-effect of having temporary see invisible (or else losing the ring or permanent intrinsic) is that you risk bumping into peaceful monsters that have made themselves invisible - this will then anger them, which might result in unwanted penalties to alignment record or a quick death at worst.
See invisible becomes most useful during the mid-game stages, where you will start encountering stalkers as well as spellcasting monsters that can render themselves invisible. Most invisible monsters can also be seen with telepathy, with the exception of mindless creatures zapped with a wand of make invisible; while having see invisible will save you the admittedly-short time it takes to blind yourself and utilize intrinsic telepathy, this is much less of a factor if you have an artifact source of extrinsic telepathy.
Towards the mid- and late game, most monsters will be able to see invisible, making invisibility less effective against them in comparison to the early game; displacement becomes proportionately more viable as a result, though neither are truly necessary to complete the game.
In SLASH'EM, there are various new monsters that can see invisible, and the property itself becomes somewhat more important: pixies are a form of nymph that appear in the early game, always generate as invisible and can rob you blind before you get your bearings; they are also capable of seeing invisible themselves, meaning that you cannot fool them by turning invisible yourself.
SLASH'EM also has invisible items, which can only be seen with the see invisible property; invisible weapons give +3 to-hit versus monsters which cannot see invisible. While invisible items are generated very infrequently, pack rats and other loot-scavenging players will want see invisible in order to make their treasure hunting somewhat easier.