From Pre-Renewal

Professor are the transcendent version of Sages. Through rebirth, Professor gain class-defining SP manipulative skills such as Soul Exhale, Indulge, and Soul Siphon. The two former skills enable Professor to act as endless sources of SP, which makes them a favorable class for party play. The third SP-manipulating skill, Soul Siphon, allows Professor to offensively eliminate all of their opponent's SP, making Professor a formidable class for PvP and WoE.