I'm putting this thread together to help out those who don't know how stealth works. Most of the stuff in here I tested myself over the past few months and posted in various threads. This will be a localized place for all that information.
Let's start with how stealth and awareness levels are determined.
Equation for Stealth level: Stealth level = Character level + level of stealth skill used (shadow walk or escape) + Cat-like Tread
Awareness level = Character Level + Sharp observer skill + Detection potion
For most Awareness level will be just their character level as only sins get sharp observer and the potions aren't cheap.
To see a stealthed assassin your awareness level must EQUAL or be greater than their stealth level.
Example: A level 60 assassin with 7 Cat like tread and 10 shadow walk has a level of 84 in stealth. This means any player level 84 and above can see him.
An assassin level 66 with level 6 sharp observer has an awareness level of 84 and will see the level 60 assassin. At 65 he would only have 83 awareness levels and would not see the 60 Assassin.
Detection potions as taken from my testing and written in another thread:
my sin is 61 with 5 levels of cat-like tread and 8 levels of shadow walk
61 + 10 + 8 =79
first subject was a 58 veno. veno could not see me alone (obviously). if the pot was correct, he should still not be able to see me
58 + 20 = 78
78 < 79
after using the pot this veno was able to see me however, supporting that the pot did give 30 levels.
a 44 veno could not see me before nor after using the pot
44 + 20 = 64
44 + 30 = 74
both are < 79
at 78 could not see me. a 79 player could.
This shows that they add 30 levels though the description says 20. Detection potions allow non-assassins to see stealthed assassin of their level or lower. A Level 93 archer using a detection potion will see any sin 93 and lower. He will not see a 94 or higher sin though.
Stealth Detection Potions do NOT work for assassins as they do NOT stack with Sharp Observer
With the addition of sage/demon shadow escape, it is possible for an assassin to be invisible to everyone (except seekers now with the newest skills) due to receiving 11 stealth levels while using it. Note that sage/demon Shadow Walk do NOT get a bonus level added and remain +10. The maximum Stealth level you can attain is now 136. Level 105 + 11 Shadow Escape sage/demon + 20 from Cat-Like Tread. Stealth detection pots and the Sharp Observer skill will no longer be enough to see an Assassin that is equal your level and uses Sage/Demon Shadow Escape.
The only class that can currently detect a level 105 Shadow Escaped Assassin is the Seeker class. For the Seeker to achieve this they must have the Radiant Sight skill. This raises the seekers detection level by 31, allowing a level 105 seeker to attain the necessary 136 Detection to see the assassin. I do not at this time know if this skill will stack with a Stealth Detection potion, but seeing as they don't stack with Sharp Observer I doubt they will stack with this skill either.
Nifty things to use stealth for and other miscellaneous information:
You can use any skill while stealthed without breaking stealth (unless you cause damage doing said skill) EXCEPT for one: Sage/Demon Spark. Use of this skill will remove your stealthed condition at the Start of the cast. You are not placed in combat and may re-stealth after if you wish.
As previously stated, you may use Healing trance and remain stealthed while channeling. You will be placed in combat, however, so make note that your mana regen will be 1/4 and you will NOT be able to use Shadow Walk to remove stealth while in combat (you can still smack something to remove stealth).
Shadow Escape can be used to reset your threat level in boss fights against bosses that are not level 150. In order to reset your threat level the boss MUST be attacking you directly. If you just use Shadow Escape and the boss is not targeting you, it will NOT reset your threat level. I like to use this when doing BH. Note that in Twilight Temple all bosses are level 150 so this will not work in here.
Shadow Escape can also be used to pull monsters from a group. aggro the monster and run. Have another member of your squad grab the monster you want then you shadow escape making all the other monsters go back to their spawn point. Make sure your cleric knows not to heal you while you do this or the monsters.
Shadow Escape can also be used to do BH runs unwined. This is very tricky and requires an experienced team. The sin runs ahead of the squad getting aggro on every mob with the squad following behind. Once you reach a safe spot where no monsters are Shadow Escape and the monsters will reset. Again this is very difficult for people not experienced and for most this will just end in squad wipes.
I hope that I shall always possess firmness and virtue enough to maintain what I consider the most enviable of title, the character of an honest man. -George Washington