My PCs knocked Filge into the negatives, then stablized him. I think they learned it's sometimes better to question NPCs rather than kill them--they learned this the hard way when they coup-de-graced Kullen & Co (the only PCs who remembered they needed to ask about the Land skeletons were both unconscious).
They've since turned Filge in to the garrison, & are contemplating whether to confront Smenk or just head into Dourstone mine w/o speaking to him.
What I think I'll do is have Natalo Bask (from AoWO) get Sheriff Cubbin to arrest the PCs for the murders of his brother (Merovinn) & Kullen & co. Smenk of course is behind this--he's pissed about his lackeys being slain, as well as the whole Filge situation. To top it off, Filge will be tranported to the jail & placed in a cell with the PCs, much to their annoyance.
A few hours after their arrest, someone will go the PCs' bail--they'll think it's Allustan at first, & they'll receive a note to meet their benefactor for dinner at the Hungry Gar. Turns out, it'll be Smenk--he makes a deal with them--he'll get the witnesses to the PCs' crimes to recant in return for keeping his involvement with the Ebon Triad secret. This way, he brings down the Ebon Triad in DL, gets an opportunity to snatch Dourstone's holdings, & keeps his nose clean.
Hell, I may even have him secure Filge's release & have him join them in the mine--they need the help, after all. The paladin won't be too happy about it, though.
To follow up, I did have Filge join the party in Dourstone Mine, as the player playing the party mage had left the game at that time (though he did come back, eventually). Filge ended up taking control of one of the Hextorian's troglodyte zombies, which the party named "Herman." Then, after clearing out the Hextorian lair, as the party prepared to rest, one of my players surprised me: trying to portray Filge as destestable & sleazy, I kept having him make overtures to the lone female character; eventally, he invited her to join him in Kendra & Garras's room for some "wine." Unexpectedly, she agreed, and spent the night with him, while "Herman" stood guard. She awoke feeling the effects of filth fever (IIRC) from a previous battle, leading one of the other PCs to speculate that "Herman" may have also been involved.
My group is playing in a modern world-version of AoW, and in ours, Filge was a creepy Smart Hero/Mage with some major power (Animate Dead is still 5th level in Modern, but that means he needs to be a 9th-level Mage/3rd-level Smart Hero. It's lucky we're bumping onto 6th level by now, or we'd be toast.).
After a short firefight, we managed to rifle-butt him to the ground, and ransack his belongings for evidence. After quickly quizzing our group's mage on how to stop him casting spells, my character ground his fingers into paste with military boots, and he's been all duct-taped up and shipped back to the Hoffmann Institute's 'special labs'. But I have a feeling he might come back... the good bad guys usually do.