Habim is a Firewitch. He is the Heart-Thread of Mathew, and is the other tutor of Safi and Iseult.
He is the co-owner of Mathew's coffee shop chain, and helps Mathew in tutoring Safi and Iseult. Although not directly mentioned, it seems as though he is working for Dom Eron alongside his Heart-Thread.
He is described as being Iseult's favorite tutor. Unlike his Heart-Thread, Mathew, Habim is stoic and level-headed in a crisis. He has the same protective instinct as Iseult, and so he teaches her to protect Safi. Habim was responsible for the girls' physical training and battle strategy. He helped Iseult hone her range in detecting Threads.