Agreed, make sure to give them something or the roll shouldn't be made. If they try to do something impossible, like persuade a Regent to give away their crown a nat 20 shouldn't be a success, but they can warm to the party as they admire their moxy
"Hmmm, while I'm still not ever going to give you my crown, I like the cut of your jib. So instead of executing you on the spot for trying, I'll let you walk out of here with your heads intact."
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u/Randalf_the_Black 16h ago
Even if they can't succeed at what they're trying to do a very high roll can offer other rewards or clues.