I'm trying to build this as a quick oneshot to try out DC20. Mostly just looking to test it out but their default campaign is soooo cheesy.

For those unfamiliar, The King Dressed in Yellow is a play, and anyone who reads the script for this play goes mad. So the idea is that people who went mad reading the script are trying to perform the play to summon the King Dressed in Yellow. (which would be bad)

I have a rough outline of

• quick skirmish at the start in the guardhouse (the fantasy equivalent of the DMV)
• leading the adventurers to where the cultists are having tryouts for roles in the play (small "dungeon"), where they find some prisoners being forced to become actors
• leading to a final boss fight that I want to have on stage during the play to a whole audience of enthralled patrons about to be sacrificed to the King Dressed in Yellow

Mostly I'm looking for ideas for theater cultists, and the boss fight. I don't want them to fight the King Dressed in Yellow, (it's a level 1 oneshot) but I was thinking about some ways to make the fight interesting and most importantly stop the play so he isn't summoned.

I was kinda thinking they walk in from stage right and a big fake foyer is on stage while the King Dressed in Yellow is trying to enter the world. I figure there will be some baddies, three of them holding props, and after every round of combat after everybody had their turn. The King Dressed in Yellow knocks on the fake front door from another plane of existence and the right prop holder has to say the right line and then the script continues. Three correct line deliveries and the adventurers lose, The King Dressed in Yellow enters the world and causes havoc. So they have to kill/steal from/silence the correct actors and stall the play while the fight is going on.

any ideas/questions would be welcome.