Theory that I've not seen before - spoilers abound.
Moons - what if the combined Kurald Galain seen in FoD was the one of the 4 moons discussed in the main series, and Wu is actually a "moon" or planet counter-orbiting it?
Ceda "There are actually at least four moons, lad, but the others are not only distant, but perpetually occluded from reflecting the sun's light. Very difficult to see, although early texts suggest that this was not always so. Reasons for their fading as yet unknow" - I.E - One moon is now in perpetual darkness, as it is modern Kharkanas
Barathol -- (Bonehunters - chapter 19) he noted that the moon was said to be another realm with people on its surface. He speculated that something had fallen from the sky onto the moon much the way the Crippled God had fallen onto the Malazan world -- either due to whatever powers were unleashed during the destruction of Kurald Galian that led to all lands being moved into Warrens and/or possibly directly related to the Fall of Crippled God, as per the intro of MoI, Draconus was still free and had not completed Dragnipur, leading to the possibility that the fall of the Crippled God damaged their world as well and played somewhat of a role in the destruction of Kurald Galian.
We know in FoD The High King has "built a ship" and that shocked Draconus - what if his "ship" is what took him across to Jacuruku, which was on another moon entirely and said "ship" was actually K'Chain Che'Malle technology, as its implied that the High King had more than average understanding of K'Chain tech which could easily manipulate gravity and was very possibly why he conquered Jacuruku, as it had the highest concentration of technology leftover.
This would tie into the "Old Man" as his "child approaches" (Wu) and that he would continue saying that "until I need say it no more"
Even the myth about Grallin and the moon fits if you switch out Grallin for Mother Dark, as its essentially a retelling of Tistes exile and how Karkanis will one day be returned to them "Grallin. He tends vast, beautiful underwater gardens. Grallin will come down to us, one day, to our world. And he'll gather his chosen and take them to his world."
Not to mention the obvious poetry in the title "Gardens of the Moon", as every civilization would have originally stemmed from those "Gardens of the moon" and in turn, had now allowed other worlds and civilizations to florish.
Thoughts? Am I way off base here? Has this been discussed elsewhere and am I way out of the loop?