In Season 2, Skills are now learned through a new UI rather than through a NPC in town, this allows players to instantly gain skills and makes it easier to view skill trees in an organized view. The skills available to learn are shown with a + on the skill. The skill tree is divided into tiers depending on the level required to get the first level of skill as shown below.
New skills are now available through equipment. New items that drop from mobs can be enchanted onto a piece of armor or weapon that make these new skills available for use along with normal skills.
DNA is also now learned through a new UI rather than an NPC; also, there is no cost to change your DNA from the new UI. Once the DNA is learned, it is automatically applied to the corresponding skills.