For Plot Reasons™, the PCs challenge, or are challenged by, a vastly higher-level opponent to an exhibition match(1) of some sort. Maybe an elder gold dragon wants to test the PCs' mettle before giving them a quest; maybe the local gladiatorial arena has a prize too good to pass up; maybe an arch-lich will only hand over a critical artifact if the PCs demonstrate they're strong enough to handle it.
Whatever the reason, the PCs need to fight an opponent of a far, far higher level than them. The opponent will face the PCs themselves; they either don't want to send a minion to fight in their place, or don't have any. However, the opponent's intention isn't to wipe the floor with the PCs; they genuinely want to see what the PCs are capable of.
How can I build a winnable encounter against a vastly overpowered opponent in a way that's fun, challenging, and mechanically interesting for the PCs?
Note: This question is about Pathfinder 2e, which does not have bounded accuracy like D&D 5e. A typical PC will miss most attacks against a creature only a few levels higher than them, and since a nat20 is not a guaranteed success in PF2e, it may be impossible to hit the vastly overpowered opponents in this question under ordinary circumstances.
I've tried various methods in past campaigns, but none of them managed to be all of fun, challenging, and mechanically interesting. Fighting directly isn't challenging or mechanically interesting, since the PCs have effectively no chance to even hit, much less win; while the opponent is likely to take out the whole party in a round or two. Leveling the opponent down isn't challenging, and sacrifices the fun of facing a powerful opponent while also breaking immersion. Fudging on the fly isn't mechanically interesting, since the players can't collect reliable information to strategize with; and worse, it can feel patronizing or like the PCs didn't earn their win, taking away the fun of the match.
I've also tried making the match not a battle to KO, but rather a strategy challenge such as reducing the opponent to half health, reaching a goalpost first, capturing a flag, etc. This isn't a solution on its own, since even if the PCs have the most brilliant strategy in the world, the opponent will likely still brute-force a win thanks to vastly higher stats. However, it can reduce the impact of some of the most unbalanced mechanics, like the PCs being incapable of landing a hit except on a nat 20, or the opponent's high HP making the fight a slog.
(1) For the purposes of this question, an exhibition match:
- Is not a fight to the death; the participants do not want to kill each other
- Is not used by the powerful opponent to merely curb-stomp the PCs
- Allows the PCs to demonstrate their skills/prowess/strength/whatever to the opponent
- Must be between the PCs and the powerful opponent, not a minion or other stand-in
- Must be possible for the PCs to win, if difficult.
Best Answer
Run it not as a combat, but via a Victory Point Subsystem (from the GMG)
If you want to run it like a combat, then @user2754's answer is probably the only way to make it work. So don't run it like a combat - use a subsystem! The Gamemastery Guide (GMG) has many example subsystems. We can use the framework established there to create one for your cinematic encounter. We know this is a good time to use a subsystem, because (from GMG's Deciding to Use a Subsystem):
And that's exactly what we are looking for - a significant moment with a different style of play than normal.
The System
We'll create a system really quickly here - they are pretty easy to set up, as explained in Victory Points in the GMG. We'll call our victory points Trial Points, and the arch-lich/dragon/etc. the Trial-Giver.
Step 1: Diminishing or Accumulating Trial Points
You can use Diminishing Victory Points to emphasize "well, no, you can't actually beat this thing. Your goal is to impress the trial-giver by staying in the 'fight' as long as possible." If you go this route, be clear with your PC's up front that the goal is to last as long as possible. This is the route I would prefer to take - I would then scale rewards based upon how many rounds they last.
You can also use Accumulating Victory Points - this is what most subsystems use. You then have the feeling of "How quickly can you impress the Trial-Giver"? It doesn't convey the overwhelming superiority of the Trial Giver as much, so I prefer the Diminishing Victory Points here. The rest of my suggestion will be with Diminishing Trial Points in mind, but it's pretty easy to flip around.
Step 2: How Long of an Encounter
See Setting your Scale - this seems like a good option for Long Encounter, where the once the VP threshold is reached, the trial-giver goes for different tactics, shaking up the DCs. I'd probably opt for a starting pool of 2 VPs per party member - that'll give you several rounds unless everyone critically fails right off the bat.
Step 3: Set Your DC's Based on the Trial-Giver's Expectations
This allows you to bypass the question of "well, you'll never be able to hit that AC, so what are we even doing." The trial-giver knows you can't beat them or even hit them. But given they are looking to evaluate the adventurers, this allows you to set the DC based upon expectations. (See Difficulty Classes for DC info). Here are some basic recommendations:
In each phase, I'd increment the difficulty level of any repeated check (but separately for the phases) - so the first attack roll in Phase 1 is Hard, then Very Hard, etc. This makes your PC's try new things, and is easily seen as the Trial-Giver trying to test the limits of their abilities.
Step 4: Determine Rewards
I'm guessing you'll always want to give them the quest, so I'd suggest giving them that as long as they last one round. Then I'd give them bonuses based on how long they last that in someway reflect the Trial-Giver's favor, so something like this:
Step 5: Run the Session
Have fun! Be clear with your PC's in advance of what's happening, reward clever thinking or use of feats, get really into the narration (and let your PCs as well).
An Option to Convey Even More The Overwhelming Power of the Trial-Giver
Terrible title, not great, but this idea came to me when thinking more about @arete's comment on using multiple pools of Trial Points. Paizo discusses something similar in Multiple Point Subsystems. Depending on the nature of the trail, you could run it like a "race". If you want it to narratively be like a combat, have the PC's continue as above, but instead of just having X rounds to accomplish it, have the Trial-Giver get a turn instead. Have the Trial-Giver roll against the same DC the PC's roll against - given their overwhelming superiority, they should basically always critically succeed. If that's the case (more likely if the Trial Giver is 10+ levels ahead of the PCs), then you can really just use it as a round marker - the Trial-Giver will get two Trial Points every round. If you have the party race them to 9 Trial Points, that gives the players 5 rounds (as long as you have the Trial-Giver go after them), assuming the Trial-Giver doesn't roll natural 1's. Regardless, seeing the Trial-Giver critically succeed at everything should leave the PC's in an appropriate amount of awe, without having to nerf the Trial-Giver at all - we're just taking advantage that 10 over the DC and 30 over the DC mean the same thing.
My Experience
I've used subsystems a few times before, and they've worked well for my games. This seems like a golden opportunity for one. They tend to be more successful if you are more transparent with your players how they work.