Berserker is one of the three locked classes in the beginning of the game. A berserker is like a mix between warriors and guardians. It does damage, like a warrior, but can also tank, like a guardian, albeit not as well. While a warrior does high, steady damage, a berserker does high, burst damage.
To unlock a berserker, you need 1,300 reputation. Reputation can be gained (or lost) by leveling up and doing quests. Some quests can either give you reputation, no reputation, or make you lose reputation. As soon as 1,300 reputation is reached, the berserker will automatically be unlocked at character selection screen.
While Warriors are high, steady damagers, Berserkers are completely different. They have skills that produce a sudden burst of damage at once. This sudden burst of damage helps take down bosses and enemies quickly with the least amount of hits as possible. But to balance it out, Berserkers have low mana as well as high-consumption mana skills. This encourages strategy as to how a Berserker can take down a boss, but conserve mana at the same time.
A Berserker typically wields a greatsword, light armor, and either a helmet or a hat. Like any other class, A Berserker is also able to wear two rings and a necklace in addition to a back decoration and skill manual. Either light boots or heavy boots can be equipped too.
A Berserker is a high damage character with decent armor, and thus, should be in the front row. Like a warrior, a Berserker does high damage, but a Berserker can hit an enemy many times in one turn. If you like seeing large numbers above an enemy's head, then a Berserker is definitely recommended as an alternative to a Warrior.