This is an in depth article on how Stealth works.
What does stealth do
Entering stealth makes it difficult for other creatures to see you. Stealth does not end if a creature spots you. Instead, the creature "briefly catches sight of you" and will get your exact location at that moment. After that, the creature will slowly lose track of you over several turns, assuming you remain unspotted. Enemies will attempt to attack you based on their guess of where you are, with a 2/3 miss chance if they can't see you. Their guess is randomly chosen based on your last spotted location, but it is weighted toward your current, unseen location. Even if you teleport away, they will have some idea of which direction you went.
How Detection works
Creatures have a chance to spot you on each of their actions. How likely they are to spot you depends on the difference between your stealth power and their "see stealth" score. Stealth power is largely determined your cS as (Level/2 + Cunning/4 + Item bonuses) varies from 0–50, plus any bonuses from or .talent level and Cunning. See stealth is 0–50
Characters can not normally stealth in heavy or massive armor. However, only armor on your "body" influences your armor. This means one point inis great as it enables metal helms, boots and gloves.
Stealth may be ended by cancelling Stealth sustain. Otherwise, stealth ends if you make any melee, ranged, or unarmed attack, or use almost any non-instant talent or ability. The non-instant abilities that can be used without breaking stealth are:
Traps are a special case. They have a percentage chance of cancelling stealth when used depending on talent level and Cunning, capping at 100%.