Lord Kintamazu is one of the Rahjs. He is mainly a researcher at heart, helping the Hengal Neogi to some unknown extent to put crystalls in the skull of people to let them mutate and was probably also in a deal with the local redcap.
As far as we know he has terrible battle magic (as his brother Lord Kinekoro comments when all the Rahjis do a burst divination). This point is pretty impressive when one of his battle magic spells is teleporting a part of the brain out of someone's skull. That definitely shows that all of the four Rahjs are truly powerful individuals, each in their own respective fields.
Also of note is that when confronted by the party Lord Kintamazu first used spells to hinder and slow them down, before nearly casting his Decerebrate spell (which Reginald Black's diplomacy managed to prevent).
He also has different eyes to the other Rahjs, for whatever reason, despite one of them being a blood relative.