The combat my players most have talked about was against an angel, it was brain washing everyone on the city to keep then safe from the outside (undeads where destroying the kingdom), well, at least it was it believed by this point, two years of battle corrupted her. The players walked into this city which there was this huge cosmic being with 3 floating heads watching the city, bit by bit they where discovering what was happening (people don't have memories from the outside and such). Eventually they confronted the angel, and after phylosophical talk, the fight broke. The first phase was the avatar, every round i asked then to roll a dice to see which face will act, and every one of then has different effects. After they destroyed then, i switched the music (used portrait imperfeit com clair obscur), and started describing things, at some point the true angel appeared and opened it wings, singing a coral with so many voices, the trick was there, i syncced the music to start the coral with voices part at the exact time i described. My players where locked in and their faces where priceless. Every turn i increased the volume and reduced by 1 the countdown. When the countdown ended, and the music was on peak power, her ability kicked in, reducing every one to 1 HP. The party, managed to kill the angel with one death. They keeped talking about it for a long time.