If we can staunch the bleeding of the Behemoth after taming it, it would be very useful for dealing with the lava flow.
As for the Crown, the truth is surprisingly useful.
1) The vast majority of Uly's power is derived from our N/A artifact, Ambition
2) It has DRM, so most people cannot use it, even Zao. Uly was just lucky that he was born with the correct attributes (Solarness) to bypass the DRM, which was one of the reasons why Zao chose him as his heir.
3) It's an Aritfact N/A weapon capable of elevating a DB's power to match that of an Anathema
4) The visual effect is the result of using one of Ambition's evocations
This is also probably the best time to show off the crown, if we want to do so. They would be extremely happy with us for saving them from the army, as well as the effect that seeing us solo it would have. Also, by publicly using it to save lives, it would make a good impression, as compared to us using it later when we could have used it now. Of course, the hardliners would not be convinced, but its not them we need to care about, so much as the hearts and minds of those who are yet undecided or wavering.