How does Stealth work in D&D?
In 4th edition
- You can stealth after any movement, but only with superior cover or total concealment
- You must beat passive perception, and reroll for any movement greater than 2 squares
- You have to stay quiet, maintain regular cover/concealment, and not draw attention to yourself to remain stealthed
- Creatures can discover you by making an active perception check or by entering your square
- Any action you take that breaks stealth only does so at the end of the action
Stealth can be used at the end of any action that allows movement. If you use a power that lets you move as part of it, or you take any sort of move action, you are able to attempt a stealth check at the end of it. Note that if you move more than 2 squares prior to attempting the check, you get a -5 penalty to your roll. If you run, the penalty is -10.
You can only become stealthed if you have superior cover or total concealment, which you can gain from hiding behind a wall, ducking down behind an obstacle, being invisible, or some other power or feature. Certain class builds, such as the cunning sneak Rogue, change it so you only need to have normal cover or concealment to become stealthed. Note that the cover you gain from standing behind allies doesn't count, and you will only be stealthed to creatures that you have cover or concealment from. Anyone that can see you clearly will still be able to see you, even if someone else cannot. These rules do not necessarily apply outside of combat, where a creature might be more distracted.
Make a stealth roll, and if your result beats a creature's passive perception, you're stealthed. They cannot see you nor do they know what square you occupy. This is different from something like invisibility where you cannot be seen but they still know your square, but you can attempt a stealth check while invisible to hide your location. Creatures you are hidden from must guess where you are (to discourage metagaming, it may be a good idea to roll a die to determine which square is targeted).
You remain stealthed so long as you maintain normal cover or concealment, so you can duck down behind a box to stealth, then stand and be partially obscured by it to remain stealthed. If you take any action in which you move more than 2 squares, you must make a new stealth check with the usual -5 penalty, or -10 penalty if you run. You have to beat passive perception again to remain stealthed. You must also keep quiet. If you speak louder than a whisper or if you do something that draws attention to you, you're revealed. Note that attacking counts as drawing attention to yourself, so you lose stealth after attacking something.
Creatures can also attempt to find you. If a creature on their turn makes an active perception check and beats your stealth check, they discover you. If a creature tries to enter your square, they discover you.
If any action you yourself take causes you to be revealed, such as drawing attention to yourself by attacking, or moving out of cover, you lose stealth at the end of the action that revealed you. For example, the Rogue power Deft Strike allows you to move before attacking. If you use the power from behind cover and move out of cover to be adjacent to a creature, you will still be stealthed for the attack and thus have combat advantage. You are only revealed once the attack is resolved and the action ends.