Yeah, I think there was a bit that may have been glossed over...
I was hinting in the conversation you had with Usqual al-Shakari that his side of the jann vs. jann tribal conflict – the anti-civilization Shakaris – lost a relatively recent battle against the jann of Khaldun oasis – the Khaldunis who seem to have very unusual magic and once dwelled in Qaybar/Ubar (mythical city of the jann).
I also eluded to his Sheikh, Ja'afar al-Din al-Shakari, having made a temporary alliance with robed outsider mages who didn't come through in the fight like the Shakari were counting. This was the fight in which the jann Sheikh Ja'afar al-Din al-Shakari was taken captive.
Hope that helps.