[@Caits] It does have a weakness: 

Mind Spike(A Class): This allows him to cause both physical and mental damage, whilst siphoning a portion of their magical energy for himself. Casting this causes a random wound to open on himself, the strength of the cast dictates the strength of the wound.

It injures himself whilst returning part of the energy needed to cast to himself. Casting a really damaging version would cause near fatal wounds on himself and his opponent. If it needs anything else, do let me know in-case I wasn't clear enough.