The roper visible in the upper-right corner is a stand-in for the yochlol they fought once before; the structure in the back is the actual Iron Garrison building itself, long standing in ruin. The players went in knowing this would be a tough fight — but as it turned out, they had little trouble with the baddies visible here. The troll and cyclopses on the far bridge had orders to stay at their posts until the heroes got close or attacked, but even if they'd waded in, the heroes are tough enough that even these big bruisers are mostly cannon-fodder for them. The yochlol fled before they could engage it, taking the leader of the drow with it, abandoning all the drow warriors to be slaughtered as part of machinations of drow politics.
There were some interesting tactical bits that caught my attention. The drow on the rope-bridge had plans to cut it down, dumping any heroes who might try to cross it into the river and herding the rest towards the stone bridge at the back — except that the heroes made a point of blowing the whole thing up with a fireball on the first round, leaving the drow a bit confused as to what to do next (especially when a well-placed wind wall prevented them from firing their crossbows at laurie_robey's sorcerer, which was their back-up plan). Also, the troll and cyclopses on the stone bridge in the rear were intended to act as muscle for the big baddies lurking in the Iron Garrison itself, but hantamouse's ranger very deliberately pulled them back to the covered area near the heroes' entry point — which was probably a critically-important move.
For the real threat was the half-dragon fire giant and his giant cleric backup lurking within the Iron Garrison itself, who had been waiting the whole time for all of the rest of the foes to soften up the heroes (and for the heroes' buffs to expire or otherwise get used up) before engaging them. His plan was not to come out until the heroes reached the stone bridge, but thanks to the ranger, once the heroes got to the stone bridge, they were "just" facing the two fire giants, instead of the two fire giants, a bladerager troll, and two cyclopses!
The fire giants were plenty, of course. The half-dragon fire giant started the battle facing jamesbarrett's weapon master alone on the bridge, and unloaded a 15d6 breath weapon on him, and then started carving him up with a 3d6+18 flaming greatsword. (Luckily, the weapon master was wearing a ring of fire resistance, which saved his bacon two or three times during the fight.) The fire giant also managed to get in a (brief) monologue, in which he announced that he was claiming revenge for the death of his half-brother Azarr Kul, the big baddie from Red Hand of Doom — yes, they've now killed another of Tiamat's children — and proclaiming with a certain amount of outrage, "This is OUR world! NOT YOURS!"
His breath weapon very nearly brought down both the weapon master and Braegli, the dwarf cleric whom they've been helping out the whole time and who insisted on coming along for the final battle; the fire giant cleric did his best to assist by using a custom ability that did fire damage in a 30' radius while healing any creature with a [fire] descriptor for the same amount, but he kept rolling so badly that the damage bounced off the players' various magical fire resistances, and the healing to the boss was negligible. In the last round of the fight, it was very much a matter of the fire giant or the weapon master — both had single-digit hit points, and the fire giant's breath weapon had recharged for another 15d6 blast, but the weapon master's turn came up first, and the fire giant went down! The cleric, while still relatively tough, went down fast once he was alone against the might of the entire party. And so it was that the Hammer of Urthat-Ghan was recovered!
They took the Hammer of Urthat-Ghan back to the Temple of Moradin and reconsecrated it, at which point Braegli's spells immediately flooded back to him and he dinged a level on the spot. The heroes were then led back to the Hammerfist Holds, where they were hailed as mighty heroes of which the bards would sing, and there was a magnificent dwarf-style party.
From here, they have to decide what to do next ... it's clear that the fire giants are seeking the prison of the Fire Titan, somewhere under the lost dwarven city of Urthat-Ghan, and have been operating under the assumption that the dwarves know where it is. The dwarves, on the other hand, have been searching for Urthat-Ghan themselves without luck, as their mission from the gods is to keep the Fire Titan imprisoned, which they can't really do until they find him. On the other hand, they've been away from Brindol for several days now, and have no idea what may be developing on the surface. They have a stone of recall that will allow them to teleport back and forth by burning a 3rd level arcane spell slot, but before they leave the Hammerfist Holds, sirfox's cleric wants to try some attempts at divination with Lathander to find out what he can about Urthat-Ghan, since Moradin seems so strangely quiet on the subject.
 This is D&D — I feel no guilt about stealing names from other sources for an evening of monster-killin' around the table!