What if there was a game mode/mini game called dungeon (maybe raid)?
Dungeon would require you to battle certain number of battles (i think ~20) with every battle getting harder and harder and giving better rewards, with last battle GUARANTEEING an arcane traitstone (chosen or random one).
There could also be other interference like having to use certain class and hero in your team for desired dungeons. Or dungeon requiring difficulty of warlord x (x=1,2,3,4) to enter/complete.
Thoughts?