- Calculate how many rounds a normal skill challenge would take at maximum, if all rolls contribute either one success or one failure.
- Add the number of complete rounds to the number of failures needed to fail, but also add one failure per round that passes without the PC:s completing the challenge.
Example: A complexity 5 challenge requires 12 successes before 3 failures. Thus the maximum number of rolls is 14 (11 successes, 2 failures, the 14:th roll decides the outcome either way). A five player party would complete two rounds and be at their third when the challenge completes.
Thus, the modified skill challenge requires 12 successes before 5 failures.
If the PC:s only roll for primary skills without any tricks, this is mathematically identical to the core skill challenge rules, but it opens up several possibilities:
- You can have secondary skills that grant bonuses to primary skill checks, but rolling for them takes you closer to getting an "extra" failure for taking an extra round.
- Spending action points to roll for those secondary skills becomes interesting, turning skill challenges from a "free" half-step towards the next milestone into an actual encounter that drains resources.
- Skill rolls where success/failure count as two of whatever you rolled become more attractive.
- And of course, a counter-incentive to skipping your turn, since you're usually not better off not rolling now, even if your skills are bad for the situation.
I think I might try this for the next skill challenge I run.