When Eddie had the Merlin Glass show him possible futures of the Droods, one of them was the hall in ruins. Maybe it's one of those things like in the Nightside, where one of the possible futures is the dread dead world where only insect monsters remain.
In which case Eddie would be able to find a way to undo everything.
In theory and if the author is willing of course

You know every time I watch Bloody Mallory (epic movie and you should all watch it) and Mallory's demon ex husband shows up I have to think of Roger Morningstar.
If there is ever a series or movie of the books they should find that actor, make him learn English (if he doesn't already speak it) and get him to play the role
Of course, the movie also has a floaty demon castle in a dimension of it's own and a ghoulville so it's no wonder every time I watch it I think of Secret Histories

i would love to see a cross over to the deathstalker series with this. i mean hes done it before tying the hawk and fisher series back to blue moon, and shadows fall to practically every other series. and it would be interesting to note that ethel does bear a striking resemblance to the metallic gel entity that continually pops up in the deathstalker series... you know, the one that we discover owen created as he was hurtling backward in time when he created the maze.... it has always seemed to me that the maze bears a striking resemlance to ethel and the heart what with all the "strange matter"... maybe i just cant let go of the deathstalker universe; it has always been my favorite. or maybe we can now see eddie and john team up in the nightside. you do realize that he could plausibly find the answers with his "sight". and eddie has gone to the nightside once already. so many possibilities....

thought of another scenario also... what if the original heart, since it did seem kind of a childish bully type, especially when exposed by ethel, came back and created anther family to strike back at the droods for turning on him? it is possible since the original heart wasnt exactly dead. eddie just broke its link to this dimension. what if it found a way back? also, what if it was the one who started the whole "satanic conspiracy" in motion, knowing that sooner or later the droods were going to have to leave en masse to another dimension in order to fight the satanists in their castle? you would think that the original heart could easily plan that one out since it is the one entity that knows every single drood secret... it would know the location of the satanist castle as well, and would be able to anticipate the droods having to send a large army there.

also, just thought of this, does anybody else see the strange corellation between the threat of the influence machine (of which there seems to have never been one), and the events surrounding a certain leader of a certain country and his (WMD's) , which also seem to have never been found... ? maybe its early, no coffee yet, but i can see the strange similarity. but it could be nothing but paranoia on my part... the reason it made me wonder is how both seemingly non-existent threats seemed to motivate two normally unmovable entities into definitive action. i guess all it takes is a well placed lie... ?

I do not belive they are all gone if the hall was destroyed then eddie would've known at once ethel would have told him remember one book he was in the Amazon jungle when the hall came under attack so there is something else going on my guess is the halls doomsday defense sent them somewhere if the hall really was destroyed then ethel also would have been destroyed and eddie would not have his Armor so yes I can't wait a few more weeks and we will see I also want to start a write in campaign to all the movie studio's and tell them about simons books half the movies now suck who comes up with theses ideas???? The smurfs really come on in maybe.coming into some money and I would risk it all on a simon green movie

Definitely this. I think there was probably a fight/battle/war, potentially caused by infighting from all the different groups in the family, that caused everyone that wasn't dead to be shifted into another parallel plane.