[@Jbcool]

Well, Fio'Ui is pursing knowledge of Chaos because he believes it to be a highly unstable but highly potent energy source of some kind that the backwards and superstitious humans mistakenly worship as a god/gods. The promise of 'Daemonhood' to Fio'Ui would translate to something more along the lines as an ascension to becoming a being of pure energy... a transformation that he would have to witness for himself in order to study and try to understand, if not undergo himself.

For the Tua'va of course... the Tau Empire needs to get as much information on this dangerous energy source as possible after all.