Its pretty much normal missions or arcade runs with a timer to mark how long you take to complete it.

There are two modes:

• Doom timer: a limited amount of time per level is set (based on what difficulty you choose), if the time runs out, the mission ends no matter where you are, a few seconds are lost for each monster you leave behind, but monsters can also drop time orbs that add a couple of seconds to your timer.
• Speed run: you just do the mission normally, and a timer keeps track of how long you take to complete each level. In the end you are ranked in a leaderboard (with separate ranks for solo and group runs) based on the total time you spent to complete the level.

How it works on:

• the missions: you choose a mission and a timer mode, and go.
• the arcade: you pick a tier to start, and a tier to end (like from the moorcroft manor/tier 2 subtown to emberlight/tier 3 subtown), then pick a timer mode and go.

A few things that change in the timer modes:

• There is that party button in the start of all levels (like in the "save winterfest" mission)

I had this idea because some time ago, me and a guildmate tried to complete a royal jelly run while the server was waiting to reboot. We had something between 20 and 30 minutes to complete it. We managed to complete the run by a few seconds (we had to skip the 4th key room, and the server rebooted right after we got to the elevator).