Soul Magic by L.M. Brown

When Orion joins an established coven of powerful mages he is unsure how he will fit into the group. The four elemental mages have had centuries to build both their powers and their relationships while Orion is little more than a stranger.
As a light mage, Orion has the power to heal, but as he comes to know the other members of the coven, he learns that not all wounds are visible, and healing tortured souls and broken hearts isn’t as easy as fixing broken bones. Orion must bring them all together before they tear themselves apart.
Only when the coven is strong will they be able to welcome the dark mage who will complete the circle and give them the power to defeat a mage who has waited centuries to exact revenge on the former members of his coven.