In Rappelz, when you have red name, you get about 10% exp per kill, 100% JP, and lose about twice the amount of exp per death. What most people don't know or don't realize is that because you only gain 10% exp per kill, you also only use 10% of the stamina you normally would. In effect, for each kill with stamina, you would gain 20% exp, 200% JP and use only 10% of the stamina. With this event going on, it would be 30% exp, 300% JP, 15% stamina use.

For example, soloing moon on your level(rappelz rupees) 50 Druid, you can gain a whopping 1k JP per kill at the expense of like 10-15 stam and low enough exp that you do not need to die too often to maintain your level.

While when can you do it. It is the time you want to OB without leveling up too quickly, or when there are some very attractive skills on your second job skill tree within first 20-25 levels you want ASAP, such as Dark Spiral, Shuddering Flame at level(Rappelz powerleveling) 20, or Yak/Petrify at level 25.