A Skill is an attack or ability. Each class has a number of skills, divided into one of three Skill Trees. Each time a character levels up, they gain a skill point, which may be spent on acquiring or upgrading a skill. Every six levels, a new set of skills become available, which my be invested in if the player has invested in its prerequisite skills, higher up the skill tree.
Most skills can be categorized as an attack, such as dealing increased damage, an ability, such as being able to teleport, or a passive ability, such as permanent increased accuracy.
Some skill may have their power increased by Synergies.
Each class has thirty different skills to choose from, and may have two assigned to mouse buttons at any one time.