Shadow of the Mad King ACT 4 -Attend the Party, starts at 9:00 AM PDT/16:00 GMT on October 31, and will run until November 1 (afternoon PDT/19:00 GMT). Once Phase 4 starts, the Ascent to Madness dungeon will no longer be available – but you will still be able to enter the Mad King’s realm, including the Labyrinth, the Clocktower, Reaper’s Rumble and Lunatic Inquisition.
The event will continue to run every few minutes all day long so everyone can get their hat and achievement. It seams that you have to wait ~ 40 minutes between events.
The event starts in Lion’s Arch – Grand Piazza with the game: Your Mad King says
All you have to do is to listen to Mad King and do (type) what he says. If you are not sure what to type just look at the right side of your screen (screenshot no.1). You will get achievement Attend the Party and the chest even if you missed some of his commands. Unfortunately, you can be disconnected from the server during the event, and you’ll have to wait for a new event to start in order to get your rewards!.
Wooded Kingdom Moons in Super Mario Odyssey