User blog comment:Septan96/Which race and job class would you be if you were transported to New World?/@comment-27008999-20151012180601/@comment-1846146-20151012232448

It's simple. Ainz bought Avatara in the cash shop. And they are not NPC or Mercenaries. They could be created through magic as hekkaran said. They are entities. Items. Loot. Not alive to have lvl's.