First, a few items I'd throw into the mix. Any powerful magical item would have been used against them by the main characters, and since the players have already fought the Big Bad, let's rule all that stuff out. That leaves the trinkets and the things that would have been useless against the PCs. Such as:
> A Cloud Keel (A&EG?) for building an airship. Useless in the Underdark, so they never bothered building the ship itself, but the PCs could probably do something with it. Heck, Dylrath could use it as a giant Outgrabe if need be. The beauty of this is that it's just a large, curved piece of magical wood. Without any context, it'll be difficult to figure out what it does, and they won't have enough Legend Lores to figure out everything on day one.
> Several magical cloaks that glamer the wearer to look like a peasant (see also the "Cloak of the Servant" and spell Servant's Guise off the WotC website). Cheap, but useful; the ghouls have used these to sneak into places like Akin's Throat and Mrid without being noticed.
> A bunch of Talent Conversion items (Mind's Eye), which allows a psion to spend a talent (cantrip) to cast one he doesn't know. Such as a magical coin that when flipped casts inkling. These items are great for psionic characters, utterly useless for anyone else, and too cheap to be worth much as treasure.
And now the RBDM part:
IMC, I once created a magical merchant guild which had expanded to interplanar levels. Besides having the best magical artisans and diviners in existence, they also had a crack team of lawyers and accountants. Basically, cross Wal-Mart, FedEx, AT&T, Lloyd's of London, H&R Block, and a Ferrari dealership and you'd get something approaching them. Alignmentwise they were pretty much LN.
Throwing them into the campaign was pretty fun, and it allowed me to see this situation from the other side. After all, the classic fantasy method of "steal anything that isn't nailed down" is a bit antiquated.
There's a ton of treasure in the ghoul city. BUT, much of it belonged to someone, before it was taken by the ghouls. How long before the inhabitants of Mrid who escaped start demanding their treasures back? Or all the other races displaced by the ghouls, or the races (like the deep gnomes) who had to go to extraordinary lengths to save themselves? Don't they deserve to get their share?
And then there are the less legitimate claimants. While the party would need months to catalog all of the valuables, every high-level priest or arcane caster in the world is going to look at the White Kingdom, and see a chance for some high-end looting. Ioun, for example, probably knows the party succeeded as soon as they did, and he'd have a BIG motivation to send some "fundraisers" down to the Underdark. I wouldn't put it above some of the churches in the world to do the same; after all, if their gods tell them "the White Kingdom has fallen!" they'll be really quick to see the practical side. The Church of Aeos, for example, is probably short on resources after its extended war against the Necromancers... if they send Sendings to Malachite and Mara demanding a tithe, what happens?
At the lower extreme, the other inhabitants of the Underdark may do the same. A few of the more adventurous have probably been following the party most of the way. There are probably also a bunch of outsiders who would like to do the same, although planar travel might still be difficult.
So, I'd expect the remains of the White Kingdom to be crawling with treasure seekers within a day at most. Are the players actually going to try forcing off a mob of people who might actually be MORE entitled to the treasures than the PCs themselves are? "Finders keepers" isn't exactly a Lawful sentiment, to begin with. If the PCs find some expensive artwork and a duergar shows up yelling "hey, that's mine!" and he's telling the truth, what'll they do?
As for the law side of this:
> To become a ghoul, you must die permanently (i.e., not resurrected). In most cases, the transformation to ghoul after this point is not intended, and is therefore irrelevant. Contracts are not usually written with the possibility of undeath in mind.
> Therefore, your worldly belongings would have passed in ownership to your next of kin; if no kin were available, your belongings would be held for public auction to cover any debts, and the remainder would pass to the city.
> Ergo, the ghouls only "owned" what they made or harvested for themselves after death. Having no post-death descendants, this property falls to their conquerors. It won't be much, though. A thirst for blood and big claws tend to keep you from being too artistic.
> Items owned by a ghoul before death, however, are considered stolen property, as are any acquired by the ghoul army as it expanded, unless the person CHOSE to be a ghoul, in which case owndership would remain with them.
> The Defenders of Daybreak, then, are simply acting as salvage agents after the fact, which entitles them to compensation of 10% of the market value, no more, in a form of compensation acceptable to the items' original owners. Typically, this compensation is liquid (cash, gems).
After all, if someone robs your house and the police catch the robber, the cops don't get to keep your stuff.
