User blog comment:Septan96/Which race and job class would you be if you were transported to New World?/@comment-27008999-20151012181203

There are 3 "grade-type" of classes in YGGDRASIL: base, high and rare. Base classes can be leveled up to 15, high classes up to 10 and rare classes up to 5.

If you want the class "overlord" or a rare class (like eclipse) you need to have a certain level in the base (at least 10) and completely maxed out in the high class (as far as I know). Ainz is a great example, since he was roleplaying as an overlord.