There are three primary classes, each with two subclasses. It is important to choose wisely because the weapons and skills available to each class are limited.
The Templars are holy warriors, sworn to drive demonkind from their land and seal shut the Hellgate forever. The Templars are the only faction that have organized a resistance to the demon invaders, and have absorbed the remnant forces of humanity into a military hierarchy of their own. The Templar classes emphasize combat prowess and primarily use melee weapons, in some combination with shields, one-handed firearms, or the grapple gun. The subclasses of Templar are Guardian and Blademaster.
The Guardian class train in more defensive skills that encourage the use of classic sword and shield fighting styles.
The Blademaster class is more offensively oriented, and can learn to dual-wield blades to attack. Blademasters may also used ranged weaponry, making them very versatile and combative in their attacks.
The Hunters are a non-faction of survivors, with their own reasons for surviving; some are mercenaries, some scientists, and some simply bewildered and making the best of things. Though lacking an ideology and distrustful of that of the Templars, they cooperate when it clearly benefits themselves. Both subclasses are able to use standard projectile weapons, and can train stealth and sabotage tactics.
The Marksman is the standard soldier, relying primarily on ranged weapons. The Majority of marksman skills are stances to improve accuracy or evasion.
The Engineer has similar capabilities to the marksman. They are able to use ranged weapons, but they have a versatile skill set. Their skills allow the creation of drones to slow the approach of enemies, as well as attack robots.
The Cabal are an occult order who studied demonic magic and adopted it themselves in order to fight fire with fire. They believe that Hell's approach is inevitable, so humanity must learn to master it, and one day may become the invaders in the demon realms. The Cabal and Templar strongly disagree with each other's means and methods, but are on humanity's side in the war with the demons, and so must work together, but usually as a strict exchange of favors.
The Summoner draws forth elemental and demonic spirits into forms that can do battle for them. They may gather a horde of monsters, or bind a single stronger being, all with a variety of properties and functions. They also have the ability to cast curses on enemies, weakening them and draining both life and power.
Evokers channel their magic energy into purely lethal force, and attack with fire, lightning, bone, spirit, poison, or vampirism. Though they can use guns, their magic attacks require a focus item, and Evokers can learn to dual-wield these to cast magic from both hands.