Strength: Increases the base damage for melee weapons.
Dexterity: Increases your chance to critical hit, and damage dealt when you critical hit. It also reduces damage when enemies critical hit you. The effects are subject to a diminishing return formula.
Vitality: Increases the base defense for armor. For every 25 stat points you have in vitality, you gain +1 to Life Regen. Every Level Up you will gain an amount of life equal to your base vitality.
Intelligence: Increases the base effect for charms. For every 25 stat points you have in intelligence, you gain +1 Mana Regen. Every Level Up you will gain an amount of mana equal to your base intelligence