The dragon considers Zilfin its mountain. Possibly not all of Zilfin! It's possible it knew about the skaven below it and was OK with that before they gassed it. But, regardless, Zilfin is
de facto the dragon's home. Belegar also considers that place part of his home; the conquest of K8P will not be complete until he is King of Karag Zilfin. There is some conflict here.
Like, ideally it would be nice to exchange gifts and become allies, that would be awesome, but
@Redshirt Army's original proposal was "we will pay you X money and provide Y service in exchange for you acknowledging the dwarves as the owners of Zilfin and letting them live in the parts you aren't directly using." For a disputed-ownership real-estate case, this seems pretty legit; two parties have a claim on a piece of property, the one that currently
possesses the property in question accepts compensation and a long-term lease to grant title to the other.
The specific of "guarding its hoard" is not a key part of the thing. But people were getting up in arms about how this is a tribute payment or that it's a state of vassalage. It's not; it's an
out-of-court settlement, because "court" in this case is "the battlefield."