The Hand of Merlin

Throughout the journey you should make a conscious effort to destroy cover whenever you can - otherwise you'll need to grind for this at the end.  Using abilities like Flaming Brimstone or Staggering Punch, or even spells like Meteor from Atlantes core to destroy cover.

If you need to grind, then start a game with 3 Wizards and on the first level up if you can get 1 or 2 flaming brimstones then just start destroying cover.  You should be able to get 16+ covers destroyed per fight.