Explain here how magic works.

There are two main types of magic - arcane and divine. There are also a couple types of magic that fall somewhere in between.  

Priest, Paladins, and Monks use divine magic. This magic comes directly from the gods and is granted only to the clergy.

Shamans and Druids use a modified magic that is a blend of arcane and divine. This type of magic was created by Rylum and is only used by Shamans and Druids. 

Warlocks are powered by their patron Devil or Demon making their magic a corrupted form of arcane magic not available to anyone but Warlocks. 

Everyone else uses Arcane magic that is controlled by Selorna.