So here's the situation:

Combat Droid is getting pounded in a firefight, decides to fall back and try to Stealth to hide behind some crates. There are five separate groups of enemies facing the party (some minions, some rivals).

In this case would the Stealth check be:

1. His Stealth vs a set Difficulty?

2. His Stealth vs the Perception of the nearest group (opposed check)?

3. His Stealth vs the average Perception of all enemies?

4. He just declares "I'm trying to hide", and when an enemy actively looks for him that enemy would roll Perception vs his Stealth (opposed check)

I feel like #4 makes the most sense, especially with so many different enemies involved. Basically he is trying to hide, but we won't know if he's successful until someone actively looks for him.

I'd probably use #4, but "assisted" on the enemy side, i.e.: if more than one are trained, then use the best characteristic upgraded by best skill. If one enemy is better in both, if there is at least another enemy who is trained in Perception, add a setback to the PC's roll.

For this I'd also assume one minion group = one enemy.

Well first it's an opposed roll not a set difficulty. This said the rest is really up to the GM. I typically rule whomever presses the situation that would cause a roll makes the roll. By this I mean if the player say hears guards coming to search a room he's hiding in the guards (GM) rolls since they are the ones coming to search. However if the player is trying to sneak past guards just standing around then the player would roll.

Really depends on the situation. Usually though I'd just have the player do his best to hide, telling him that such-and-such a location would grant him a Boost die or Setback die depending on visibility and other factors, and then make the check when it's relevant.

If it's during structured gameplay and he wants to hide for his turn, yeah just have him make a Stealth check vs the Perception of the NPCs that will be coming around the corner during the next round, and narrate appropriately, making note of the result for the latter turn.

A set difficulty is fine too. Not gonna break your game. So if all else fails, just pick a difficulty based on the situation at hand and roll with it.

By this I mean if the player say hears guards coming to search a room he's hiding in the guards (GM) rolls since they are the ones coming to search. However if the player is trying to sneak past guards just standing around then the player would roll.

I have the player almost always roll. If the guards are searching, the player is rolling their Stealth against the guard's Perception.

Just to clarify the situation, the five enemies were 2 Rivals, and 3 groups of 3 minions. It was structured combat, and on his turn he spent Strain to do two Maneuvers to move directly away from them (short to long range) and then said he wanted to hide using Stealth.

So like I said, at that point I felt that no rolls were necessary, and on the enemies turn if they chose to look for him to shoot at him they'd roll Perception vs his Stealth. I like whafrog's idea of providing a bonus die to the enemies because there are so many of them, so they'd probably help each other.

By this I mean if the player say hears guards coming to search a room he's hiding in the guards (GM) rolls since they are the ones coming to search. However if the player is trying to sneak past guards just standing around then the player would roll.

I have the player almost always roll. If the guards are searching, the player is rolling their Stealth against the guard's Perception.

Just to clarify the situation, the five enemies were 2 Rivals, and 3 groups of 3 minions. It was structured combat, and on his turn he spent Strain to do two Maneuvers to move directly away from them (short to long range) and then said he wanted to hide using Stealth.

So like I said, at that point I felt that no rolls were necessary, and on the enemies turn if they chose to look for him to shoot at him they'd roll Perception vs his Stealth. I like whafrog's idea of providing a bonus die to the enemies because there are so many of them, so they'd probably help each other.

1. Two maneuvers wouldn't get you from Short to Long range. It takes 2 maneuvers to move from Medium to Long range. (that is a rule I routinely forget, but I remembered this time!) ... so that could affect the narrative a lot.

2. Were they aware of the PC's presence?

• If so, then a Stealth check is absolutely a good thing to do. If he was able to get sufficient distance from the gunmen, have him roll a Stealth check vs. Perception from the NPCs with a Boost die. The dice tell you what happens. Next turn, maybe they run to look for him and he's disappeared (potential ceiling cling moment) or, if the dice roll was particularly beneficial to the PC, he could suggest that the NPCs give up the chase.
• If they weren't aware at the beginning, what is the purpose of the check? What does the PC want to happen? Find out what the goal of his check is, and then set the difficulty accordingly. If the goal is "I want to keep hiding," then tell him he's already hidden and ask him what else he'd like to do. But these checks don't exist in a vacuum; they are usually made to support the scene and to further the goals of the encounter or adventure. So if you keep that in mind, and get a sense of what the player wants to actually accomplish, the way forward should become much more clear.

1. My mistake, it might have been medium to long only, I don't remember those specifics.

2. Yes they were aware of the droid, they were in active combat with him and had shot at him (and been shot back). My concern with him rolling Stealth vs Perception is WHOSE Perception from the 5 enemies who were aware of the droid? There were other PCs involved too, so it's not like all the enemies would immediately chase.

Overall the droid PC was getting hurt a lot, so he wanted to run away and hide until the doctor could come patch him up a bit.

Who's perception should simply be the most difficult, ie the guy that's best at perception with boost dice for getting assistance. I say this because if they're all looking only the best one finding them will matter since they'd tell the rest of the group "hey I found him here"

The Stealth check would be opposed, as people have already stated. But I'd be reluctant to just let the player hide his way out of combat. At the very least I'd demand he put something big and solid (like a wall) between himself and the NPCs before allowing him a check. Then there would be setback dice for the number of NPCs present - I'd say at least one per NPC/minion group beyond the one with the highest Perception. There would also be setback dice, or even a difficulty upgrade or two, to reflect the fact that multiple people could see him well enough to shoot at just moments earlier. Unless you have some sort of invisibility field generator "hide in plain sight" is an ability better left to fantasy settings.

Of course, if the player could make the check after all this I'd let him hide, no argument. But then it would be down to what he wanted to do next. If he kept moving away, making every effort to leave rather than re-initiate combat I'd ask him for another, not-quite-that-difficult Stealth check. At this point any Advantage or Threat from the initial check might come into play in various ways. If, on the other hand, he wanted to ambush some of the NPCs from a better position, or simply take a minute to heal up or buff before getting back in the fight, I'd have him roll against the original difficulty.

The Player rolls Stealth vs Perception against the best Enemy. Add Boosts for range, cover and any other environmental difficulties (darkness, rain, whatever), add Setbacks for each additional NPC or Minion Group, and if they have any special equipment or helpful environmental effects (well lit area etc.).

To add onto FuriousGreg and Kreiger, I might do a few different things in the moment:

1) have the player suffer two strain for a maneuver to "prepare" his Stealth check, or to "interact with the environment." He'd need not only move behind cover, but utilize that cover to the best effectiveness.

2) have one of the PCs roll a Deception check to distract the enemies long enough for the droid to hide,

3) OR have the droid PC roll a Deception check to misdirect the NPCs giving chase.

But yeah, if the player wanted to pull off a "hiding in plain sight" sort of deal, like the aforementioned "ceiling cling" or "empty elevator" or hiding under a sewer manhole or whatever, it would take at least some strain for a maneuver, or a Deception to set it up, or an increased-difficulty Stealth check. Not impossible, very cinematic and fun, but difficult.