4e's rules weren't perfect, but they might be one of the best in the history of the game.
- You can make a Stealth check at the end of any movement you do, if you are in concealment, cover, or outside of sight. A "distracted" target is also valid outside of combat. You get a penalty if you move more than 10 feet or if you run. (This encourages you to move slowly; ie: "move silently.")
- When you make a Stealth check, you "target" each creature present; if your Stealth check beats their passive Perception, you're hidden from that target. Hidden in 4e means you are Silent and Invisible. You can be hidden from some creatures and not others.
- You can remain hidden as long as you have partial cover or partial concealment, as long as you keep quiet, as long as you keep still (if you move more than 10 feet, you make another Stealth check with a penalty), and don't attack. Also, as long as a creature doesn't enter your space.
- You have the benefits of being hidden while you take the action that undoes your hidden status (so if you make a bow attack, you'll stop being hidden AFTER the attack).
- Surprise can only happen when someone is actively hiding. The hiding group makes a group check against the passive Perception of all the other creatures. It's a group check, so if half the group succeeds, everyone does. Each creature the hiding group succeeds against is surprised when combat starts (if combat starts - a successful hiding group might not start a fight!). Some creatures can be surprised and others not surprised in the same fight.
I really like how the 4e rules tie stealth to
moving, since that's the thing that could change line of sight. Though in practice having to beat ALL other creatures' passive Perception meant that surprise and stealth was often pretty hard to pull off.
I also really like how hidden and invisible were different things. If you are hidden, attackers need to guess your location. But, you can be invisible without being hidden (because you're making noise, moving around, stirring up dust, etc.), and that still provides a benefit. Even if people can basically tell where you are, they still have trouble hitting you. And an area attack didn't care if you were hidden or invisible, so if you were in the area of a fireball, it was a problem, even if nobody knew you were there.
I don't really know why 5e didn't keep some of these elements. I'd wager it was hard to design Hide as an
action while also having the more free-form
movement in 5e that didn't tether moving to a distinct phase of the round. Probably not impossible, but maybe not exactly a high priority. It's less clear to me why 5e is so averse to the hidden/invisible distinction. Mmmmmaybe due to trying hard to be newbie-friendly, because the assumption is that when you "turn invisible" no one knows you're around?
