Following the cataclysm, the Sirin used their natural advantage of flight to seize absolute control over the remaining habitable peaks.
The Acoustic Covenant: The Sirin offered the surviving non-flying races a choice: submission or exile to the lower, dangerous cliff-edges.
The Feudal Bonds: In exchange for the resources needed to survive (such as timber from Bell-Keep and metals from Khaz-Gundrak), the Sirin elite used their magic to maintain the continent's acoustic infrastructure. Their giant tuning forks and wind-castles keep the toxic lower mist from rising any higher, keeping the mountain peaks safe and sunlit.