I have reached Level 21 and don't seem to be gaining experience from any of my foes towards Level 22...So I suppose they have built that in for future worlds.
Are there any monsters in Mirage that are high enough level to continue at this point? I've been looking around without much luck.
Thanks! Marcus Ghostsong 120 Myth
Max reachable rank is 22 because you can get animus from rank 16 creatures who still give xp at rank 21. There are creatures in Mirage like the 4 ghosts in Caterwaul and Shadowbones. There is a list on Duelist101.