It's a glitch. Basically you /join a location you want to glitch, then alternate between that location and another 4-6 times e.g. Let's say I want to glitch blindingsnow monsters;
*clicks house icon to teleport to my house*
*repeat 4-6 times*
When you kill the monsters, they respawn fast.
-HOWEVER, THIS ONLY WORKS IF THERE IS ANOTHER PERSON IN THE ROOM, AND WHEN YOU'RE THE ONLY PERSON LEFT IN THE ROOM, THE GLITCH EITHER STOPS OR MONSTERS STOP SPAWNING ALTOGETHER UNTIL YOU REJOIN THE ROOM.
-You have to make sure to use two(2) dashes(-) and you have to always join the same room that you intend to glitch. It can work on single/double digit rooms, but it's harder to glitch them since they're either full(so you end up in a different room, and the glitch won't be effective) or it's only you in the room(glitch won't be effective as you're the only one in the room).