There are 3 different types of Special Skills in Revelation Online. They are 1-star skills, 2-star skills and 3-star skills.
Players unlock their first 1-star special skill within the tutorial stage with Akuta at the beginning of the story. 2-star skills can be bought at the Demonslayer Bookseller Ninis Zu who can be found in Sidus Ur. To get 3-star skills, an Immortal Annex Silver ID Card is needed which will be unlocked after players finish daily quests and increase their favor with the faction. 3-star skills can also be achieved for free on the 7th consecutive login which starts automatically upon character creation.
Players can level up Special Skills by using Dao and Sigils. For every Special Skill, there is Enlightenment and Paths within the Dao Tree. Enlightenment can only be used when the Dao Tree Path is unlocked. The Dao Tree Paths are directly related to the Character Path and currently there are only 10 paths within the tree.