In order to change your class you will have to talk to priest Devin. Priest Devin is usually located in the Crywolf map. In GameOns MU , Priest Devin is in lorencia outside bar/pub.
Where his about is not available.
You must finish Marlon's Quest first before talking with Priest Devin.
The Quest items to change job can be brought in lorencia.
In order to get your 3rd class, you will have to go through 3 quests. You will have to go ask Priest Devin yourself. As far as we know he let’s you go for the ultimate test. Are you up for it?
After you finished all quests (it’s a 3-way quest), you will be rewarded with extra stat points, and your class will change to the corresponding top-tier class, listed below:
Dark Knight -> Blade Knight -> Blade Master
Elf -> Muse Elf -> High Elf
Dark Wizard -> Soul Master -> Grand Master
Magic Gladiator -> Duel Master
Dark Lord -> Lord Emperor