What Is Csst?

I'd like to know what is CSST. I did a Five-minute research but I Found nothing, so I'd hope, there would be something, that would clear it up.
TNX for replying

 

corrupted sand swept tomb,its a dungeon

 

But what is so special about it?

 

It gives a ton of XP for higher levels, people often do it in groups to level up fast.

 

xp

 

Rnx

 

the most efficient way to make xp
people throw a dungeon bomb then an xp bomb
and then speedrun the dungeon
it's usually done in parties, as then you can finish it in ~3 minutes and run it again.