I love the idea, it's something I've meant to implement.  

Will we have a mana system or some other way of controlling when we can do spells of varying power?

Also, here's the basic premise of the character:

Human from Ravnica.  Grew up in a Gruul clan, but converted later in life to Boros(picking up his third color).  He's wild, but with a sense of justice and an instinct to protect.  He is distanced from the Gruul by his willingness to protect the weak, but also from the Boros by his distaste for strict discipline.  I have not yet decided how his spark ignites.