Heaven's oasis was an extremely famous location in Damon's last life. It was kind of a dungeon, except it was a floating dungeon that kept changing its location. Only a lucky few were able to enter it, and most of those who entered came back with memory loss and no gains whatsoever.
Eventually, a dedicated few did manage to return with minor gains. The said minor gains included epic gear and a lot of good stuff. More importantly, there was a key detail that players finally managed to uncover.
The fairies in that dungeon possessed absurdly high luck stats. That made them nearly impossible to hit and even harder to kill. This was the reason why most attempts failed before reaching the inner chambers.
And even when some managed to defeat the outer guardians, the final boss was undefeated and, worse, it was capable of wiping memories.
