Colemon is Maester in service to House Arryn. He is thin and nervous, with too little hair and too much neck. Colemon was the personal maester to King’s Hand Lord Jon Arryn during his stay in King’s Landing. He treated Arryn when illness struck him, until he was sent away by Grand Maester Pycelle and Lord Jon’s illness continued to worsen.

After Jon’s death he returned to the Eyrie with the rest of Lady Lysa Arryn’s entourage. He was entrusted with constant care of Lysa’s child, young Robert Arryn, who is afflicted with a shaking sickness. Maester Colemon leeched him often to rid of his bad blood and gave him concoctions to ease his pain.