This set up thematically the other "big encounter" for the night, which was a bebelith (essentially a huge, demonic spider) lurking in the main route between the temple and the dwarf-held territories (which the group had avoided earlier by sneaking around a side entrance), placed there as a guard by the Drow clerics. (For the purposes of the game, I merged "bebelith" and "retrievers" into a single creature. Technically one is a giant, demonic spider and the other is a giant, demonic construct that looks like a spider. Whee.) However, upon hearing that these creatures were sometimes called "retrievers" because they are sent out by powerful demons to catch enemies etc., the group had an "A-ha!" moment about the question that had been bugging them of why the Drow were in the Hammerfist Holds at all -- i.e., that the whole thing is a hunt for some sort of MacGuffin.
With this realization, and since they were tapped out on spells and such for the day anyway, they made a wild "dash back for camp" via mass fly (tossing a fireball at the main camp of Drow just to cause a diversion) and had a pow-wow with Archfather Braegli, their old friend from the Red Hand of Doom days and the dwarf who'd sent them on their mission. After some correlating of facts  and a few well-placed Diplomacy checks, they managed to get out of Braegli that the whole "re-colonization of Hammerfist Holds" routine was part of a larger effort among the dwarves to reconnect with the lost dwarven civilization of Urthat-Ghan, which was tasked with keeping one of the Five Titans imprisoned under the Earth after the titans rebelled against the gods. The Drow are apparently mercenaries in the employ of the Fire Giants, who regard the particular titan under Urthat-Ghan as their sire and appear to be trying to free him -- but to do so, they have to find him, and they think the Hammerfist dwarves know how to do this (explaining the party's earlier observation that "Somebody's stealing dwarves!").
This, combined with the Frost Giant incursions on the surface (and the unnaturally severe winter affecting Elsir Vale), led them to further wonder if one or more of the other titans might not be free already, which gave Archfather Braegli the willies in no short order. sirfox's cleric joined with Braegli in a divination ritual (story hand-waving, no game mechanics required) that revealed the location of the "Hammer of Urthat-Ghan," the relic they still need to retrieve in order to restore Braegli's spellcasting abilities and thus enable the dwarves to fight off the Drow incursion ... recovering the hammer and re-consecrating the temple of Moradin will be the next tasks.
As the GM, something I was experimenting with in this particular adventure setup was a "high-level dungeon crawl" scenario; to prep the adventure I filled two sheets of graph paper with level-appropriate themed encounters, put a couple of plot MacGuffins in place (and gave them a partial map that included the location of one of them and a couple of different routes they could take), and threw the players at it to see what they would do. I wasn't terribly surprised that they immediately made for Known Plot Point (the temple itself), albeit via a side route -- this group has a history of chasing the plot and ignoring anything that isn't plot -- but I was a little surprised at how stymied they were when Unknown Plot Point (the missing hammer) didn't immediately become obvious. They did do a bit of dungeon-crawling from room to room, killing whatever they could find that seemed to need killing, but they quickly tired of this and definitely seemed inclined to avoid simply Greyhawking the place. From a game design perspective, I had set up two places where the hammer might be and simply decided that it would be in whichever one they came to first, but the party steadfastly refused to go to either place without a clear marker saying "Plot, this way -->"
So I decided to let the divination ritual work and put the hammer in a completely different place instead: in the back of a giant set piece using some miniatures-game maps I have sitting on the shelf waiting for the chance to be loved. This gives the party a chance to unload everything they've got on a large, multi-stage encounter, instead of piece-by-piece going from room to room and should suit the "Heck with exploration, cut to the action!" nature of the group.
Fortunately, we're not gaming this weekend, so I'll have time to write it up before they go in blasting!
 Fortunately, this is D&D instead of Call of Cthulhu, so no SAN checks were required -- although hantamouse seemed to have blown one anyway after the word "demon" got tossed around.