Foul expects [Linden} will attempt to rescue and cure Joan, this is why he allowed the Skest to be seen, so that she would know where to go. If Joan is cured, she may then be able to give the ring to Foul of her own will.
Should not the Demondim be taken aback by the Staff? One wet sniff should tell them that half of it is their own local boy holy grail.
Of course Jeramiah has been in the Land for a while. How else could he have done his legoland Revelstone and Mt. Thunder. Obviously Linden needs to be at Revelstone, and the Tom and Jerry show arriving a couple days after she does suggests that this was to be the meeting place. And Mt. Thunder? Well hell, don't all roads lead to Mt. Thunder? Whenever there's some nasty stuff going down, where is the first place everyone looks?
...Lord Foul is booted out from The Land,,as suggested above,,and not allowed to to come back in ( the re-closing of the arch of time) and everybody lives in death in The Land Happly Ever After.
..By titleling the series, " The last Chronicles.." I have to believe that the author ,,in time honored tradition,,liberates his characters and creations by end -never to be available to serve him again...Therefore, even with tongue in cheek ,some variant of my crystal ball vision, i feel is quite possible.....MEL