Kankoran's magic revolves around battle. Their magic thrives on the chaos of battle, action, and raw power. They are, thus Battle Mages.
They have a long-standing rivalry with the Sondeki, much of which has to to do with the fact that their magic is oppositional. Sondecki magic is controlling force and bent towards justice, so knowingly using it for injustice tends to hurt them. This can be seen especially in the Sondecki Rage, where their internal power gets out of control; if they cannot balance it, it will kill them. This is why justice is important: it represents a balance, a healing of imbalance, in the world.
Brothus corrupted the Sondecki because his own sense of justice was corrupted and he swayed many to his beliefs before the reality of it dawned on folks like Charles.
The battle lust of the Kankorans is naturally uncontrolled and thus bent towards injustice, so it ends up repelling what a Sondeki can do.
