Blue mind. Quatuor Potentiis

One of the most exclusive Siel Haless institutes of the world is located in Redwater, England. Cassandra, close to graduation, has been chosen for a weird course of study: Esotericism's Culture, of which no one seems to know anything about. Zane, her best friend, and has been secretly in love with her forever, has been chosen too, even though he was still shaken by his younger sister's loss. At the course, they both meet the attractive and arrogant professor Derek, and Melissa, a girl with a very dark style, who immediately reveals her not completely human nature. Derek tells about the absurd Dimidium's existence, the Nephilim and the Blazes' order, chosen to keep the two races hidden. Cassy's attraction to Derek tests Zane's feelings, but his friendship with Sarah makes her jealous too. What Cassy does not know is that Derek and Melissa, who seem to hate each other, are actually hiding a very huge secret, but they will not be the only ones.