Board Thread:General Discussion/@comment-190.222.194.92-20131109195307/@comment-99.235.128.59-20131111003446

It's pretty random. Battling bosses and AW's seen to give it a higher chance to level. Upgrading and clearing campaign camps also gives it a slight chance to level. Easiest way that I found is to just take a card and fight a bunch of AW's with it.