The Dark has 2 races: the Vail and the Death Eaters
Vail can be one of the following classes: Pagan, Oracle & Assassin
A Pagan is a spell caster comparable to a mage in other games.Pagans Are particularly good at AoE (Area of Effect) combat. Stick them in a group with a Warrior and an Oracle and they can burn down multiple critters quickly.
An Oracle is a healer class and an Assassin is well an assassin.

Death Eaters can be Warrior, Guardian and Hunter
A Warrior is more solo oriented, a Guardian is a group type tank, with skills to gain and hold an enemies attention, and Hunters are ranged attack specialists.
These classes are designed for group and solo, with the Oracle being most effective in a group and the Warrior, most effective outside of a group.