But come on, you know what I mean. Kellar's Keep is clearly a rip-off... er... homage to the Mines of Moria.
And the Gargoyle, despite being an old-school D&D monster, has a miniature resembling a statue of a Warhammer Bloodthirster (daemon of Chaos). Which was itself a rip-off... er... homage to the Balrog. Whip and flaming sword and all.
So why didn't this Quest Pack include some kind of encounter with a totally-not-Balrog? The Guardian at the end of the last quest doesn't cut it. How did they miss such an obvious opportunity for a ri... homage?
After seeing so many statues of Bloodthirsters throughout the HQ world, wouldn't it be a fun and scary twist to get really far into Kellar's Keep and run into the actual horror they depict? A real Bloodthirster, vastly stronger than any Gargoyle, which you could nonetheless represent with your trusty Garg model from the base game?
"This foe is beyond any of you..." RUN AWAY!

Just needs the bridge tile from Against the Ogre Horde. Or, in a pinch, grab those two double-blocked-square markers and flip them upside down to give a nice black 'abyss' on either side of a narrow bridge.