Hunter is a new monster introduced in the 10/27 update (evo2: Nightstalker, evo3: Van Helsing). His storyline has him as a vengeance-seeking humanoid out to hunt down vampires, and accordingly he wields a giant crossbow and wears a cape with potential religious symbols.
He is generally rated poorly for Dungeons and PVP because of his middling stats, lack of debuff skills, and single-target-only special attack. However, fire, water, and light Hunter fare better in PVP because of the value of single-target focused nuking in the Astroleague. Additionally, light Hunter has the rare shock skill on his basic attack, making him even more useful in the Astroleague.
Hunter can be used reasonably well in story mode and in PVP, but will fall to the wayside in mid-to-end game dungeon runs.