The Monk focuses on their inner self (i.e. self improvement). Monks are extremely fit and spend a lot of time training in unarmed combat. They also specialize with lashing type weapons (flails and nunchakus) and staff/stick weapons. They have the ability to perform "critical hits" (i.e. vulnerability strikes) to enemies using unarmed attacks and lashing attacks. These strikes can be devastating and disabiling as the Monk becomes more skilled.
In addition, the Monks have a special skill that can allow them to target specific body parts on opponents. This can be of great aid if the Monk knows various body parts are vulnerable or not as protected.
Monks also have the ability to block enemy attacks even without having a shield! If all this wasn't enough, the Monk also has a Blind Tolerance skill that helps them still be able to perform actions while blind (well, better than those without the skill).