And with special mage skill you can use magic twice per one turn.
On the adventure map your rage is getting down but mana up (mana is regenerating), so it can happen that you will start a combat with zero rage but max mana - so you can use offensive spell and if you kill some enemies - you will gain RAGE from this - so right after the offensive spell you can use your rage ability as you will have rage points now
There is as well a rage skill that can give you mana
I wonder if DEVs will add new skill that would allow to use rage twice per turn