Dream Scar

The Dream Scar, also known as Dream Arena or simply Arena, is a fighting pit accessed through the Dream Labyrinth. It was created as a sort of prison to prevent The Nightmare Beast from being released into the world. 
Every day, a different Champion fights in the Arena. The boss in the Arena changes on every Server Save, including when there are emergency shutdowns at unusual times. For this reason, it's not the same boss for all game worlds since every now and then one or another suffers extra Server Saves. You can check the current boss on all worlds here.
There are 5 bosses:
* Plagueroot
* Malofur Mangrinder
* Maxxenius
* Alptramun
* Izcandar the Banished