This Tier 3 talent can be used against "an unaware adversary". What constitutes an unaware adversary? One taken wholly by surprise? Which isn't really possible, since there is no "surprise" in Genesys, just whether you beat them in the initiative order or not. So then does it apply when you act before an opponent in a turn? Once per combat? Can you use Stealth vs. Vigilance to escape their sight and make them "unaware" of you again? How do you guys interpret this talent?

I would interpret it as being completely situational. Strict rules are just going to get in the way here, so I would have some basic options like the Stealth check, but every situation will be different.

I can imagine a social encounter where the target doesn’t think you are a threat until it’s too late, they knew you where there but didn’t know you had a knife going into their back. Do you need to have made a Deception check for that? Perhaps your crew where the distraction.

During combat it’s going to depend on the players creativity, use of Advantage or Triumph, or perhaps an opponent rolling a Despair. Manoeuvres could work too, with decent narrative description and interesting terrain features.

i feel like that will be entirely narrative. you'll simply ask the GM - "is the NPC aware that I'm here and that i'm a threat to him?" - if the answer is no, backstab!

The player most likely to take it is not extraordinarily creative, so I wanted to give her at least a couple reasonably reliable options she can go to, rather than it always be a judgment call on my part. I think an "Evade" maneuver, which could be either Deception vs. Vigilance or Stealth vs. Vigilance, could work as a means to slip into an enemy's blind spot for at least one attack. Your points are well taken, that there are a lot of possible ways to set it up, but at least for now I need an option that makes it relatively easy to employ.

Always remember the Story Point too, players who struggle with creativity often also struggle to spend Story Points. This could be an opportunity for you to offer her chances:

PC “I want to backstabb”

GM “how about spending a Story Point?”

PC “ok!”

GM “do you have an idea what it may look like?”

PC *has an invitation to be creative without the need to speak up in a group and no pressure to actually do it

If you are trying to give a player reliable options i'd go with somethings like:

• If you go before them on the first round of combat (synergy with quick strike here also)
• Story Point as @Richardbuxton pointed out, though i would be careful as you don't want this to be an option for every attack (personal opinion on the last part there)
• Talent Support, here are is a very quick and dirty example, would need playtested and balanced.
  • Fient, One tier higher than backstab. "After a melee attack, as a maneuver, make a deception check opposed by the target. Success means they are unaware for your next combat check"
    • Could move the maneuver to before the attack also

Here's what I ended up offering my player as various options for employing this talent:

Outside of RPG's and constructs such as turn order, a backstab is traditionally how a combat either starts or is avoided entirely.

Would you allow steps 1 and 2 to occur prior to combat? You have #1 worded carefully to simply say "encounter", and step 2 could certainly allude to first turn of structured play. Basically, if you sneak up on a guy before initiative is even rolled, I'd say you automatically get the first turn of the structured part of the encounter to shiv him. Then there's either someone left on the target's side or not.

I also really like #3 and #4 by the way.

I would definitely allow them outside of combat, but I still begin any actual combat (or structured gameplay) with an initiative roll. Even if you sneak flawlessly into position, there's still a chance the target might notice you (Vigilance check for initiative) at the last moment. However, either #1 or #2 potentially allows you to employ the Backstab talent even if they do notice you, by virtue of you acting first in the initiative order (#1) or having planned ahead to nail them even if they spot you at the last second (#2).

I suppose if you are using the second method, and they act first and jump off a wall or teleport away, then you might miss your chance, but I'd say those situations are pretty rare.

These methods have worked well in actual play so far; my "sneaky" player has used all four methods at this point in three game sessions, though spending a Story Point has been the most common way. Based on the reaction of the group, #3 is the most popular way, but that's only happened once so far.

I believe I misread...I thought 1 and 2 were a sequence (although I'm not sure why I didn't also think 3 and 4 were additional "steps"). Long story short: your "How To" seems like a good plan to me!

Ah, no, each one is a different option! That would be a demanding sequence. ?