Achievment system reward your expiriance throughout the game. It is made by four sections Farming(aka PvE), PVP, Clan, Others.
Farming, PvP, Clan(self explanatory). "Others" contains different other parts of the game like fishing, seeding, enchanting etc. And our personal favorite "I'm an idiot".
Inside you will find cool little progress bars tells you when you are going to compleate your task.
Those progress bars lead you to next lvl of the reward and Bigger rewards
All rewards are : Fame points
You can explore them ingame. Have fun with L2Mutiny!