Stealth

Rangers, thieves and monks can effectively become invisible by using their stealth ability, which is also known as the Hide in Shadows ability. This ability differs from invisibility in a few important ways:
* the character must pass a per round check to see if they've successfully remained hidden;
* if the state is broken as the result of a non-hostile action, the character gradually becomes visible over a 2 round period (allowing time to retreat);
* stealth is more easily broken than invisibility;
* it has an unlimited number of uses.
==Mechanics==
The stealth ability is governed by the Hide in Shadows and Move Silently skills. [In the original game, these two skills were represented by a single Stealth skill.] The starting value of these skills varies based on class, race and dexterity. See the Thieving Abilities article for more information.
In order for the stealth action icon to be enabled, the character must be wearing no armor, light armor (Robe, Leather Armor, Studded Leather) or medium armor (Hide Armor, Elven Chain Mail), though the latter has a stealth penalty. If heavy armor is worn, the stealth button will be disabled. There are a few exceptions to the rule. Both Corthala Family Armor and Mithral Chain Mail do not penalize stealth, acting like light armor despite being Chain Mails.
When a character attempts to enter stealth mode, the first condition checked is whether the character can see any hostile enemies. If hostile enemies are present, the character will fail to enter stealth. What's relevant is whether or not the character sees the enemy, not whether the enemy sees the character. For example, if a Mist Mephit blinds Imoen with a mist ball and that results in her not being able to see the mephit (or any other enemies), she can immediately enter stealth, even though the mephit can surely still see her. Shadowdancers have an improved version of the stealth ability called Hide in Plain Sight, which allows them enter stealth whether they can see enemies or not.
First, there is a check for critical failure. There is a 1% chance that stealth would fail. Any source of positive luck (Luck, Chant, Bard Song) would eliminate critical failure.
Next, the character's Hide in Shadows and Move Silently skills are averaged together and compared against the lighting at the spot where the character is standing. A character standing in shadow (or at night) has a better chance of succeeding than a character standing in light. If a character is standing in shadow, their sprite will be shaded. In darkness, the average value of both skills needs to be 100 to have 100% success chance. In light, it needs to be 200. E.g. a character with 100 in Hide in Shadows and 50 in Move Silently (average: 75) would have a 75% chance to hide successfully in darkness, but only 37.5% in light.
If these conditions pass, the character will effectively become invisible. If any condition fails, the character will have to wait one round (6 seconds) before a new attempt can be made. If the character is under a Haste effect, this is reduced to 3 seconds.
While invisible, a new skills check is made each round to determine if the character has successfully remained hidden. If the check fails, the character "leaves the shadows", slowly becoming visible again.
Like normal invisibility, the character can freely move among most enemies without risking detection. Stealth will be broken if actions other than movement are performed, such as if the character:
*interacts with the environment (e.g., opening doors/chests, picking something up, attacking, etc.) 
*uses an action icon, even if no action is ultimately performed. For example:
**swaps weapons via the quick slots (swapping from the inventory screen will not break stealth) 
**searches for traps
**uses cast (even if no spell is chosen)
**uses "use an item" (even if no item is chosen)
*travels to a new world area, including districts within a city such as traveling from the Athkatla docks to the slums
Interestingly, characters can often interact with devices without breaking stealth. Also, using a group action icon doesn't break stealth.
If stealth is broken by an aggressive action (such as setting a trap), the character immediately becomes visible. If stealth is broken by other means (such as opening a door or failing the skills check) the character has 2 rounds before they become visible. During this time, characters can avoid detection by breaking line of sight with any nearby enemies. Line of sight can be broken through movement, such as by rounding a corner, closing a door, or simply moving farther away (making increased movement speed a very desirable effect). Detection can also be avoided by using a spell, potion, or magic item to become invisible, but the line of sight must still be broken before stealth can be re-entered.
Note that a character may appear to make a failed backstab attempt that doesn't break stealth. Such attacks are purely cosmetic and occur without an actual attack roll being made. These attacks can be turned off by enabling the No Cosmetic Attacks option on the feedback screen. 
When a hidden or invisible character performs a melee attack, they receive a +4 THAC0 bonus. This bonus is unrelated to backstabbing and is therefore awarded regardless of the attacker's class, position relative to the target, or type of melee weapon used. No bonus is awarded for ranged attacks.
==Gameplay==
* Since the average of Hide in Shadows and Move Silently is used, there is no benefit to having a higher value in one over the other.
* Having both skills at 200 gets the maximum stealth ability even at daytime outdoors. However, there is still a benefit from going over 200 since it offsets the stealth penalty of wearing medium armor.
* There is always a 1% chance of failure even with 200 stealth unless negated by luck.
* A character's sprite will be shaded when they are standing in shadow.
* A blinded character is able to hide anytime, as long as no enemies are present within their extremely narrowed sight. [See Blind Thief Trick.]
* Spells and abilities that allow invisible creatures to be seen will also reveal creatures hidden in shadow.
* Stealth may or may not prevent a creature from initiating dialog; the behavior varies by situation.
==Related items==
===Stealth boosting===
The following items offer a bonus to either the Hide in Shadows or Move Silently skills.
====Armor====
*Human Flesh
*Shadow Armor
*The Night's Gift
====Boots====
*Boots of Elvenkind
*Worn Whispers
====Cloaks====
*Cloak of Elvenkind
*Drow Piwafwi Cloak
====Rings====
*Mercykiller Ring
*Ring of Duplication
====Potions====
*Potion of Perception
*Potion of Power
===AC boosting===
The following armors offer improved armor class options for stealthy characters but with a stealth penalty.
*Hide Armor (AC 6)
*Elven Chain Mail (AC 5)
*Elven Chain +1 (AC 4)
*Sylvan Chain (AC 3)
*Melodic Chain (AC 2)
*Drow Elven Chain (AC 2)
*Bladesinger Chain (AC 1)
*Aslyferund Elven Chain (AC 0)
*Drow Adamantine Chain +5 (AC 0)
*Dark Elven Chain (AC 4)
Improved versions of the Hide Armor (+1, +2 and +3) were introduced by The Black Pits II: Gladiators of Thay, but are not available to players.
==Gallery==
Coran stealth on bridge in Fourth Cloakwood (BGee).png|Coran in stealth mode scouting the bridge ahead of the party in the Fourth Cloakwood area - Can you see him? - (BG:EE)
Spider Cave western part (SoD).png|A F/M/T stealthing to scout the spiders in the western part of the Spider Cave in the Forest of Wyrms (SoD)
Coran stealthing in Cloakwood Mine level 2 (BGee).png|Checking out the enemies in Cloakwood Mine level 2 (BG:EE)
Coran scouting in Cloakwood escorted.png|Coran scouting in stealth mode ahead of the party escorted by Faldorn's Dread Wolf and Branwen's Animated Dead somewhere in the Cloakwood Forest. (BG:EE)
Category:Class abilities
Category:Game mechanics
Category:Invisibility