Keeonean was a general of the evil mage Minax. He was basically the evil equivalent of Lord British's military leader, the Paladin Dupre. He was said to be in command of the Minax Faction during the early days of the Faction wars in Felucca. Dupre stated that he respected Keeonean as a military leader.
During the attacks by Minax in 2003, following the release of the Age of Shadows expansion, Keeonean appeared again. He was captured by Britannia, and was tried. Upon his conviction, Minax appeared and killed him.
Keeonean's trial in the Court of Truth was unusual in that it appears to have been a military tribunal of some kind rather than a proper trial per se. Thus, there is Britannian legal precedent to use the Court of Truth to conduct military tribunals.