Actually, there are two events that appear identical but have somewhat different effects. One leads to Minister Koun as your Permanent Ally, while the other makes him take over a city and become completely independent. In both cases he will lead a copy of the civ to which the event happens. (Unless it has been fixed recently, in the version where he becomes completely independent he is usually quite weak as he does not get any free technologies and can never catch up to the rest of the world.) There is no way to know which version you've gotten until and unless you let him go.
Canonically, Minister Koun is a Grigori leader. (He thus has a -100 weighting towards all religions and s effectively Agnostic despite not having the trait.) I think he is a politician who took came to prominence among the Grigori after Auric killed Cassiel, but that has never been stated for certain. We do know that Cassiel never liked the kind of urban politics he practices, and that Cassiel's death upset the Grigori greatly, probably enough to allow a demagog promising vengeance against the Illians to rise to power.
