We have officially finished after only 4.5 years (including a 10-month sojourn into Ravenloft)!
Alienor Contessa Soliogn-Stark struck the final blow, destroying Nicodemus with some very accurate shooting (Sneak Attack Crit!) two turns before the spirit of William Miller was to return from the Gyre. Her shot killed ten million, but some judicious use of Wishes brought back some of those who were lost.
Taking a cue from the Ob, the Duchesses crammed in as many planes as they could, leading to this solar system:
Fire: Jiese
Life: Av & Ascetia
Air: Caeloon
Water: Mavisha (with some hitchhikers from Shabboath! oops!)
Earth: Urim & Teykfa
Space: Apet
Time: Reida & Bhoior (a ringed turtle? we're not sure on that yet)
Death: Nem & Amrou
They never landed on Iratha Ket, so it never became an option. One of the better scenes of our Gyre crawl was when they went to Nem and found an ash reproduction of the original RHC Headquarters, which had been vaporized during "The Incident." (When IronPeak threw a train into Sijhen's Gidim portal, causing a backlash of planar energy which killed thousands, including Alienor's son Mort, the player's original PC.) Alienor found the scorched shadow on the road where Mort had died, finally mourned him, and received his pocket watch as the icon of Nem (he was an Eschatologist). They bonded with Amrou by bringing along Sargon of Uggat, whose father was cup-bearer to Ur-Zababa, and helping him raid the Golden Legion treasury.
Amazing game. Thanks to Ryan Nock and EN World for making it all possible. I hope to fill in the massive gaps in the storytelling some day, but today is not that day.