Invisibility in ADOM is a special state of the PC or a monster. For both these beings the state of invisibility may be temporary and permanent, as well as intrinsic or conferred by external forces. Again, an ability to see through invisibility may be possessed by both the PC and a monster.
Invisibility for the PC 
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In ADOM v. 1.1.1 Edit
Generally, monsters which are unable to see through invisibility will not target the PC even standing near him/her for numerous turns. They, however, will tend to get close to the PC despite not being aware of his/her exact position. Thus, invisibility for the PC is an incredibly effective ability that lowers potential danger from monsters while the PC doesn't attack anything (see below). Note that cornering a monster and cutting any possible way for it to escape will cause it to attack the PC despite invisibility if the creature is in panic state.
The inability of a monster to see the invisible PC disappears as soon as the PC attacks the monster using:
- Melee weapons.
- Missile weapons or any thrown object (with several exceptions).
- Elemental ball spells, as well as wands of fireballs and wands of destruction.
- Short-range damaging spells (such as Burning Hands or Destroy Undead.
Likewise, monsters will be able to attack the PC if (s)he triggered a fireball trap explosion or a vortex explosion.
Note that only monsters affected by attacks (even if they resist the damage) will be able to "see" the invisible PC. Leaving the level or reapplying invisibility (in case it was not permanent) will not make these monsters lose sight of the PC.
Note that mindcraft and bolt spells, as well as their corresponding wands do not break invisibility effects and allow the PC to attack monsters with practically zero risk level. Several more specialized attacks will not alert monsters to the PC. These include the following:
In ADOM v. 1.2.0 Edit
Monster behavior towards the invisible PC was significantly changed in version 1.2.0 of the game. Monster will now occasionally hit the PC if they are next to him/her, although will not use any special attacks unless they actually see the PC. Taking into account the monsters' tendency to "gravitate" towards the PC such occasional attacks will happen relatively often.
Note that several types of attacks (see above) that didn't break the invisibility in version 1.1.1 were fixed in 1.2.0.
Acquiring/removing invisibility Edit
The PC can acquire the state of invisibility by one of the following ways:
- Drinking a potion of invisibility (grants temporary invisibility).
- Casting Invisibility spell on himself/herself (grants temporary invisibility).
- Wearing an item that grants invisibility (ring of invisibility, cloak of invisibility, robe of invisibility or Brannalbin's Cloak of Defense).
- Drinking from a pool (may grant temporary or permanent intrinsic invisibility).
- Eating a corpse of an invisible stalker (grants permanent intrinsic invisibility albeit with a very low probability).
To remove invisibility the PC may simply wait for it to wear off (in case it is temporary) or unequip the corresponding item. Potions of visibility will remove invisibility temporary. These potions seem to override any invisibility while their effect is active.
Note that permanent invisibility may be removed only by drinking from pools. Potions of visibility override permanent invisibility as well, but they are very rare items. You can also wear normal mummy wrappings.
Extra Edit
Dak, the Arena master, will not allow the PC to fight if (s)he is invisible. While this is generally not a problem, PCs who received intrinsic invisibility before completing Thrundarr's fourth quest will face significant difficulties. Only two ways to complete the quest for such PCs exist: either use pools to try to remove invisibility or use potions of visibility as a temporary measure. The first way is notably worse, as intrinsic invisibility is considered a very powerful ability by many players. The second approach is very unreliable, as potions of visibility are rare items and do not usually last long. Many players therefore try to complete the first 19 fights early on (even before accepting the quest itself from Thrundarr) to avoid possible trouble.
Low-level shopkeepers may take some time to spot an invisible PC within their shop. It is, thus, possible to steal some items without any risk, as the shopkeeper will not ask to pay for those items which the PC had picked up before being spotted. Usually, the message -shopkeeper- stares at your position with great intensity indicates that the PC was spotted. Note that this is obviously a chaotic act.
Players may experience some difficulties with companions which do not see through invisibility. Several in-game actions (such as swapping places (':s') or 'c'hatting) can be used to alert the companion to the PC's presence.
When the PC is invisible his standard '@'-sign is not displayed on the map (unless he also has see invisible). In this respect invisibility behaves like the blind status. The difference is that in case of an invisible player the cursor is still displayed at the players actual location, which in case of a blind player the cursor is not displayed on the map at all.
When the PC is both blind an invisible, the invisible status will not be displayed on the status line.
Invisibility can be considered to be both a status condition (because it is displayed on the status line) and an intrinsic, because it is listed on the death screen and potion of insight or Revelation screens.
Invisibility for a monster Edit
Invisible monsters are exactly what a player may expect them to be. Unless the PC is able to see through invisibility, these monsters will not be shows on the map, but will be able to attack the PC. They may be attacked with any means in return if the player deduces their location or uses area attacks.
Slaying an invisible creature earns twice as much experience as slaying the same creature if it is visible. This boost is independent of the whole fight with the monster and is accounted for only during the killing blow. It is possible to make the monster invisible just before killing it for a cheap way to increase experience gains. In version 1.1.1 this boost was calculated solely on the visibility status of the monster. As of version 1.2.0 this situation was fixed negating the experience bonus if the PC can actually see the monster.
Sources of invisibility Edit
Monsters in ADOM can turn invisible in one of the following way:
- Casting invisibility on themselves.
- Drinking a potion of invisibility from the floor (only intelligent monsters can perform this action).
- Being hit with a thrown by the PC potion of invisibility.
- Being affected by the PC casting Invisibility spell.
- Being intrinsically invisible (only invisible stalkers possess this feature).
The following monsters may cast invisibility on themselves:
Note that both the cat lord and Khelavaster may be encountered neutral, but can turn invisible before the PC actually sees them. In this case the PC can accidentally walk into them which triggers the melee attack with obviously drastic consequences. This situation was addressed in version 1.2.0.
It is possibly to temporary make a monster visible by throwing a potion of visibility into it.
