Thought I would post this just in case someone else runs across this problem. In order to destroy the skeleton transformer, you must not only have Dyson in the party, but he also has to have been given the quest at the Sun Temple.
It took me a few restarts to finally figure that out. I looked in the archives, read every hint and walkthrough I could find, but even though the rest of the party had the quest, and even though I kept the twit alive and followed all the directions, it took going to Murmerwoods and the temple, then back to the Necromancer Guild before I could destroy the thing and finish the quest.
I'm guessing I'm probably not the only person in the world that didn't tie the two together, so I hope this helps someone else!
Thanks for this site, BTW. It has saved my sanity more than once. :}