In our last session, we had a situation where the group found themselves fighting a large, droid-like enemy. Our assassin used stealth to sneak up behind the enemy and plant the thermal detonator in a wedge in the droid's back. He rolled the light ranged attack and came up with 0 successes and I think like 1 advantage. If you roll 0 successes on a thermal detonator roll even when the weapon is supposed to blow up ON the enemy, what does that mean? Was the thermal detonator a dud?

Maybe with all his attention on careful sneaking, he forgot to flick the switch to arm it...

Personally I would have allowed the successful Stealth roll to proxy for the attack roll. It doesn't make sense to me to have to use Ranged Light to place an item where you're standing.

Perhaps he didn't get it lodged in there, and the droid twisted, sending the detonator skittering across the floor, where it <something plot-driving or cinematic>.

Unfortunately yeah, it wouldn't go off. If he had enough Advantages he could have activated the Blast quality anyway.

In our last session, we had a situation where the group found themselves fighting a large, droid-like enemy. Our assassin used stealth to sneak up behind the enemy and plant the thermal detonator in a wedge in the droid's back. He rolled the light ranged attack and came up with 0 successes and I think like 1 advantage. If you roll 0 successes on a thermal detonator roll even when the weapon is supposed to blow up ON the enemy, what does that mean? Was the thermal detonator a dud?

I'm with whafrog that Light Ranged was probably not the best choice of skill however I wouldn't have included it in the Stealth roll because getting to the target unobserved is not the same thing as acting once you get there.. I would have used a Mechanics check to find a good spot to wedge it in or maybe an Skullduggery check, depends what the Droid was doing: was he just sitting there (Mech) or was he in combat or moving around (Skullduggery).

As for what happened on the result (0 Success, 1 Advantage) I'd say he wasn't able to find a suitable spot to wedge it in and still has it in hand.

If say they had 0 Success and a Threat then they dropped it and the Detonator is next to the now alerted Droid on the ground, with the timer running...

If they has 0 Successes and a Despair, well bad news... a drop and BOOM...

Edit: changed Athletics to Skullduggery

I assume the attack roll for a thermal detonator is intended to represent a character attempting to throw the detonator like a grenade. Since that's not what happened here, I concur with those who have suggested that making a Ranged (Light) roll was perhaps not appropriate. I might have charged a maneuver to plant the thing, possibly accompanied by a Mechanics skill check. I'm sure there are other ways to improve that as well. That kind of flexibility is one of the reasons I'm a fan of the game in the first place.

I'd have said Mechanics or Skulduggery (player's choice) to plant it. Him getting no successes is something I would have narrated as, "you jam the detonator into a crack, but before you can flick the arming switch the (giant droid creature) moves, and you have to tumble away to avoid getting crushed. The detonator sits there, quietly, at the back of (creature's) leg."

Then, of course, smart players would be trying to get themselves in a position to hit the detonator with a blaster bolt, causing it to explode and do damage. Remember, in this system there's no such thing as a failure, merely... shifting opportunities.

Maybe with all his attention on careful sneaking, he forgot to flick the switch to arm it...

Personally I would have allowed the successful Stealth roll to proxy for the attack roll. It doesn't make sense to me to have to use Ranged Light to place an item where you're standing.

This.

I must be confused on how explosives work then. I had him roll for the attack still to calculate damage because my understanding was that you still rolled for explosive damage for the possible chance of it doing more damage and to see how many advantages/disadvantages/threats/and despairs happen. So if he were to proxy with a successful stealth check, then we just assume that the detonator goes off, deals base damage, and absolutely no side effects happen? Because that seems even more extremely generic than having a random dud. While it is not ideal, at least it keeps things interesting. They thought they would instantly end the fight which ended up not happening by considering it a faulty thermal detonator so they had to once again become creative. I understand that a dud is more than likely not the best choice because I even spent a minute trying to rack my mind around another solution to the roll but came up unsuccessful. I just had them roll because the dice in this game are meant to help bring random actions and situations into each encounter in this game

No, you're correct a roll should be made to determine how effective the planting/Attack was, we're just suggesting a different skill such as Mechanics or Skullduggery. Others are suggesting that the Stealth roll was enough but I disagree with this, one of the reasons being exactly what you've mentioned, but the other is what I mentioned before: sneaking has nothing to do with planting an explosive. Keep in mind though that because of the narrative nature of combat rolls an especially good Stealth result will net Advantages or even a Triumph that could affect the planting roll.

Personally I would have allowed the successful Stealth roll to proxy for the attack roll. It doesn't make sense to me to have to use Ranged Light to place an item where you're standing.

Reminds me of this thread.

I think it'd be reasonable to roll the attack separately. You'd be getting a boost from the stealth to make it easier, but you'd still have to make a successful attack.

Personally I would have allowed the successful Stealth roll to proxy for the attack roll. It doesn't make sense to me to have to use Ranged Light to place an item where you're standing.

Reminds me of this thread.

I think it'd be reasonable to roll the attack separately. You'd be getting a boost from the stealth to make it easier, but you'd still have to make a successful attack.

Yes, I said basically the same thing there...

This is a matter of intent vs. "making skill check"

If you make checks with using intent, it is much easier to narrate.

For example, if your intent was to "plant and arm the detonator on the large droid without being noticed." After you stealthed over (easy enough to narrate success/failure), use the intent to narrate.

Failure can then mean that you either did not get to plant the device OR you did not get to arm it. When you fail, you do not get your intent, you get something else.

With 1 Advantage, there is little you can gain from the situation, maybe its just that you get out of the way before the droid reacts and accidentally stomps on you.

With threat, I might even say you armed the device, but it did not stick and it is not rolling around the room... enjoy!

One of the principles I use when GMing is from Luke Crane's Burning Wheel games - "say yes or roll the dice". I don't make the PCs roll for something unless I have a clear idea of the stakes, and there is a clear risk of failure.

In this scenario, I wouldn't bother making the PC roll the attack, because it doesn't seem likely that he could fail once the detonator was placed. I would just assume that it was an automatic success (with 1 net success, if I needed to calculate damage). I wouldn't even bother working out damage; I'd just say that the thermal detonator would automatically destroy the droid-like thing.

There's not much point in creating a potentially weird situation like this; it doesn't enhance the story, engage the players, or create tension, so just let it go without a roll.

...I wouldn't have included it in the Stealth roll because getting to the target unobserved is not the same thing as acting once you get there.. I would have used a Mechanics check to find a good spot to wedge it in or maybe an Skullduggery check, depends what the Droid was doing: was he just sitting there (Mech) or was he in combat or moving around (Skullduggery).

Agree, much better. Plus, that way the successes and advantages are directly applicable to the detonator going off.