Keyes

Ki-Su is a Mage of the Dark Guild Tartarus and a member of the Nine Demon Gate.

Appearance
Ki-Su, as his alias "Black Monk" suggests, dresses in a form-fitting robes with a high collar. The robe itself has a checkered pattern, and covers a collared shirt and tie that Ki-Su wears beneath. Around his face and on his head, Ki-Su wears an ornate head piece, this covering his jaw and fanning out over his head almost like a crown.

Most notably though, Ki-Su does not have a human face. Instead, his body seems to be that of a skeleton, with Ki-Su possessing no nose, eyes or skin.

Tartarus arc
Ki-Su gathers with his fellow Nine Demon Gate members at the Tartaros headquarters. As they convene, the group are joined by Kyouka and Silver, both of whom were off on "special missions". Hearing that two of their other members, Jackal and Tempesta, are also out, the group move to put their plans against the Magic world into action.

After hearing about Jackal's successful assassination of the entire Magic Council, Ki-Su listens as some of the other Nine Demon Gate members argue over their lack of participation in the plan so far, though he chooses to remain out of the conversation, instead silently commenting about their dedication to Zeref.