As I mentioned over in the throat-slitting kills thread, I personally handle attacks against unaware targets as being at -1 difficulty die. My justification being that the regular difficulty pools listed seem to have active, aware combat in mind, and I personally feel that an unaware target should represent a lower difficulty to hit than one who is actively attempting not to be injured.

However, I freely admit that I'm a fairly generous GM (even if "unaware" attacks are incredibly limited in how often they can be made - likely once per encounter, unless the player is sneaking around a lot). If I didn't downgrade the difficulty, I'd likely give the player one or two boost die and then allow them to aim on top of that.

Other players have suggested using a stealth check in place of creating any solid rule for unaware combatants, and then simply using any advantages gained from sneaking around as boost dice on the surprise attack.

EDIT: Well, I misread entirely. You're discussing initiative. Ignore me then. :x

I've just added boost dice during initiative. Combat is supposed to be abstract and narrative. Rounds and actions aren't taking place by roll, they are taking place simultaneously. This means that even if the PCs some how lose out on the rolls and they all end up going after the victims of their ambush, then the targets realized they were walking into a trap and managed to get their shots off while coming under fire. Just because you haven't rolled yet doesn't mean you haven't started shooting. It just means you won't mechanically hit.

GM: "Alright, you're all set up in ambush positions. Roll discipline for initiative, plus two boost dice each since you have superior position and know they are coming. The Trandoshans will roll vigilance."

[Rolls]

PC: "Dang. How did we all roll blanks? No successes for any of us."

GM: "The bounty hunters walk slowly down the dusty desert canyon, their captured mark in tow. You watch patiently from above, confident that you have them in your trap. Suddenly, their Trandoshan leader stops, sniffs the air, and holds up a closed fist, indicating to his team to halt. You open fire, but it is too late. The gang scatters behind the rocks for cover while spraying the cliffs with blaster bolts. One catches you in the leg before you manage to line up a clear shot."

See? Mechanically, the enemy might still go first, but you can still describe the scene as the PCs initiating combat. Basically, the system encourages you to combine the traditional stealth/perception rolls and initiative rolls used to determine "surprise rounds" all into one roll.

To make sure the ambush goes off properly without being noticed, I'd do an opposed check: the ambushers' might be Stealth, Deception, or Cool depending on the nature of the ambush; the defenders would be Cool, Perception or Vigilance.

My suggestions:

Give a Boost or two to the ambushers and a Setback or two to the victims for their actions in the first round of combat only if the ambushers win. If the defenders win, there's not an effectively-executed ambush.

Or limit the defenders to one Maneuver, period, for the first turn, and they can't buy more with Strain, representing being surprised.

Or upgrade the difficulty of the defenders' dice once, for the first turn only.

I'm guessing the reason why there is no mechanic benefit per RAW is because the PCs will also be on the receiving end of whatever mechanic you use. It's a fairly lethal system already. I'd probably offer PCs doing an ambush a boost die or more if the ambush was set up with good prior successes on Stealth, Discipline, or Leadership. This way I don't have to necessarily give NPCs the same boost.

I do Vigilance vs Stealth for initiative for the ambushed. The ambushers roll initiative as normal.

I do Vigilance vs Stealth for initiative for the ambushed. The ambushers roll initiative as normal.

Vigilance against Stealth makes a lot of sense, but it can be tricky sometimes. For example, if a party of four PCs with widely disparate Stealth skill values are all crouched in ambush, do you use the worst Stealth value among the group, because that character would be the noisiest? That would be totally justifiable, but it does hamper the party's overall chances of ever pulling off an ambush together.

That depends on the situation. If they are sneaking up on the fly, then lowest. If they have time to set things up, then standard cooperating rules.

My initial plan was to give successful ambushers a free round of attacks, like a lot of games do. Someone pointed out that an awful lot can happen in a round in this game, and this could give too much of an advantage. Perhaps instead, successes on the stealth roll could translate directly into extra successes (or boost dice) on the initiative roll. Advantages on the stealth roll could be used as usual, granting boost dice to actions or free maneuvers. Making a really good stealth check would mean you almost certainly win initiative over most of the enemy, often with some extra tactical advantage, but the enemy at least has a chance to respond.

Yeah, stealth can add boost the the initiative check, which is usually going to be Vigilance on the part of the ambushee and Cool for the ambusher.

This was discussed at length over here:

http://www.d20radio.com/forums/viewtopic.php?f=149&t=12456

One of the things that cam up that people sometimes forget is that just because you rolled the initiative and can go first doesn't mean you'd get to do anything valuable to the combat.

So if for example you're being ambushed, and you come out in the top initiative slot...so what? The other guys are still hidden from you. They haven't' made a move to reveal themselves. Even if you make a perception check to see if anyone's there, but that's your action so no shooting for... You can fire blindly into the bushes for no reason, but the check difficulty will be equally ridiculous... Maybe take cover because you have a bad feeling?

See just because you get to go first doesn't mean you get to start the combat.

Someone with a good stealth skill could also - according to the skill text - improve allied stealth checks, it doesn't specify how, but it does point out that a good result can let the stealthy character point out helpful details to allies, I'd assume that's a boost die or so, depending on result.

My 2 cents :

Success in the ambush add challenge dice to the initiative pool of the enemy.

And If you've succeeded with a critical, you earn a free action at the very start of the combat turn.

Something I've been thinking about:
When a check calls for "cool" players are free to roll vigilance, but if some participants in the fight are rolling cool and others are rolling vigilance (whether by choice or not), all those rolling cool get a boost die added to their initiative pool. This incentivises rolling cool whenever possible, and further gives an advantage to the ambushers when one side is not aware of the other. Further, advantage gained from a successful stealth check can add further boost die to the initiative check.

Secondly, if combat begins with one side unaware of the other, from the result of a successful stealth check, the difficulty for hitting the unaware parties is reduced by one until they have acted (Much like being "flat footed" in D&D), so long as the attackers remain hidden. (Example: a Wookiee marauder breaking from cover to charge a stormtrooper patrol would *not* receive the decreased difficulty of hitting the stormtroopers, as they would easily see him coming, and thus be prepared for his attacks.) To get into melee range would require a new stealth check.

I think these rules give a substantial advantage to ambushers during the first round, while still being relatively simple. Is it too much of an advantage though?