I have an idea for an encounter that takes place in the PC's dreams... The twist is that after so many rounds (3 or 5) the whole encounter changes between 2 or 3 maps. I feel this can put in any lvl adventure. Make each "dream" the same length. End the encounter when they finish the "dream". Have the PC's choose finish one dream unknowingly, also set deferent rewords if you have the "dreams" different difficultys.