Wrathchild
Veteran XV
it made sense that it'd be another thing you could unlock as you continued to play, but from what i've read you can pretty much unlock everything in a week of very moderate play so...Maybe they are planning to raise the level cap and continue to add unlockables in the future. That would make sense since you are capped at 20 right now.
I played for about 5 hours and made level 9, have about 80% of the content unlocked unless there is hidden stuff too.