Sneaking is a basic ability all characters are allowed to do. Sneaking can be improved through leveling the ability score, or by using equipment, which buffs it. Sneaking can be started by using the Hot Key "C" (by default) or clicking the sneak button on the UI. When a character enters into sneak mode, areas that are not seen by NPCs are shaded with a dark color, whereas any LOS cone belonging to an NPC is seen in a red colored hue. If you enter into an area which is within a NPC's LOS your sneaking will fail and they will see you.
Sneak Ability[]
You're perfectly able to sneak without any levels in the ability; adding ranks simply makes sneaking easier. The higher the character's sneak, the smaller the LOS cone of enemies. Your sneak skill also reduces the AP cost of entering sneak in combat, becoming 1 AP at level 5 (which is particularly important for making full use of the Guerrilla talent). There does not appear to be any benefit to raising sneak above 5.
| Sneak | AP Cost | Enemy Sight Cone |
|---|---|---|
| 0 | 6 | ~85 degrees |
| 1 | 5 | ~70 degrees |
| 2 | 4 | ~55 degrees |
| 3 | 3 | ~40 degrees |
| 4 | 2 | ~25 degrees |
| 5 | 1 | ~10 degrees |
Moving into Restricted areas[]
When a character is in sneak mode, it allows the character to move into restricted areas (i.e. a person's bedroom or the legions armory). Also, the character is allowed to open/close doors and even lockpick doors in this state. If a Line-of-Sight cone of an NPC intersects the character, the stealth is broken prompting a message stating "sneaking failed". If this occurs in a restricted area or while attempting to steal or lockpick, the NPC will remove you from the area, or a fight will begin.
Stealing[]
If an NPC is in a room with the character(s), stealing items without sneaking is impossible; even when their back is turned, they will notice the theft. When the character enters stealth mode, it allows them to move around the room, stealing any and all items they want without any ramifications (permitted the player stays out of the LOS cone of any NPCs). In order for a character to be able to pick an NPC's pocket, the character must be in stealth mode to do so.
Enemy Vision and AI[]
The line of sight cone has approximately a 10-12 meter limit, for most creatures. This depends on their perception and any bonuses to sight they have, but in general, enemies cannot see very far. This allows a long-distance crossbow user, for example, to re-enter stealth after every attack.
The AI also poorly handles all their opponents being invisible or sneaking. Rather than looking around, they simply end their turn early (unless they have something useful to do like heal an ally). This allows a player to always enter stealth before finishing each character's turn to avoid all enemy attacks. They won't be discovered unless the foe turns toward them due to a missed attack, or by fluke (and the enemy rarely lines up their sight accurately enough by accident when the player's stealth is high). This exploit can lead to very boring play, however... the player generally faces no threats because the AI has been short-circuited.
Attacking from Stealth[]
Using any attack or skill will break you out of sneak (as will many items that act like spells, such as food and voodoo dolls, but curiously not potions). Simply attempting to use a skill or spell will exit stealth mode before the skill can activate. However, standard weapon attacks hit before canceling sneak, so you can get a hit in while stealthed. This is important for the Guerrilla trait, for example, as well as sneaky murder (see below). You can re-enter stealth immediately after, so long as no enemy or NPC has turned its sight cone toward you (which can happen on a missed attack, as part of the target's dodge animation).
Invisibility[]
An invisible character is able to act with relative impunity (steal, open chests, etc.), similar to being in sneak mode but without line of sight cones. Further, being invisible allows you to enter sneak mode and attack while sneaked, even while enemies are looking directly at you. However, being invisible doesn't count as being in sneak mode, for the purposes of the Guerrilla talent (use the invisibility to enter sneak mode).
Attacks and skill use will end invisibility, using the same rules as sneaking.
Sneaky Murder[]
If you want to kill a character without triggering combat with anyone else or losing reputation, you need to perform a one-hit kill from stealth. A weapon attack while sneaking or invisible will not trigger reputation loss or hostility as long as no one sees you and the attack kills the target. Even in a crowded room with NPCs surrounding the target and looking at them, the lethal blow won't get you in trouble because the target isn't alive to cry foul (and no one saw YOU do it). It helps to start invisible if you can't get into sneak mode in the right position, as some crowded areas are tricky.
This can be done against hostile enemies that haven't seen you, or against friendly or neutral NPCs. Whole hostile mobs or friendly towns can be cleared out this way without ever being noticed, so long as you don't miss and your attacks kill in one hit.
This works well in the early game, where one-hit kills are possible with the right buffs and equipment, but it falls apart in mid- or late-game when enemies and NPCs take many attacks to bring down, and a one-hit blow is unlikely. You can sometimes reduce a target's health without triggering a fight. Some NPCs will allow you to hit them several times before actually becoming hostile (though it's a gamble). Sometimes you can also use neutral (not recognized as coming from you) effects to reduce a target's HP before you attack them, such as tricking them into walking through burning oil or poison.
Repositioning NPCs[]
The spell 
Feather Drop does not trigger hostility. It can be used to move annoying NPCs away so they cannot witness theft or violence, or to move a victim into an isolated area where you can murder them without witnesses, or start a fight without the whole town joining in. You can also trap NPCs into areas they cannot escape, such as a prison cell or an enclosure made of boxes.
You can also drop NPCs into dangerous terrain like Fire, Poison or Lava. This will not trigger hostility, as they do not make the connection between your using Feather Drop and their taking damage from the hazard. You can use the hazard in this way to lower their HP before delivering the final blow yourself for the XP reward.
Detecting and Force-Breaking Stealth[]
Taking any form of damage while sneaking or invisible seems to break a character out of stealth. This includes damage from physical or magic attacks, harmful surfaces (poison, fire, etc.), and status effects (burning, poison... not sure on Rot). Essentially anything that provokes a pain animation in the character (damage that actually heals them due to high resistance does not break stealth—though this needs confirmation). This is useful against sneaky enemies since a simple fireball or poisoned surface can flush them out. However, it is also a source of trouble for sneaky players since even 1 damage from any source will shock them back into visibility.
Other ways of detecting stealth include the movement pathing—if you sweep the mouse back and forth over a distant area and see the line showing your move path taking a sudden, freak shift around a bare patch of ground, that's a good indication of an invisible character hiding there.
Shooting with arrows or zapping with magic projectiles can also detect stealth. Target the ground by holding CTRL for arrows.
Sneaking Skill & Gear[]
There are several ways to boost your Sneak ability, outside of ability points. You shouldn't need more than 1 or 2 ranks from ability points.
- Sneaking gains a +1 bonus from the Cautious Trait.
- You can find or craft Helmets and Boots that offer a +1 Sneaking bonus.
- With level 5 Crafting, Void Essences can be combined with any apparel for +1 sneak.
Related Talents[]
- Backstabber: Good synergy with sneaking (since being behind a foe enables sneaking frequently), but only if using daggers/knives.
- Guerrilla: Doubles your weapon attack damage while sneaking.
- Speedcreeper: Move at normal speed while sneaking.