Found after the first battle with Erintrah.

My minions' foray into the Oblivion King's deserted castle has paid off. Those that managed to return brought back a cache of notes. Information on a strange poison (the Lich called it "bacteria") that modified the nature of zombies was of no interest to me, and I sold it to the hag Crulicar in exchange for materials necessary for my experiments.

My focus was on the Oblivion King's research into an indestructible golem (he ultimately rejects that word, but his early notes use it and I will continue to), referred to as "Vain". Research into the golem's origins suggests something of "Daemonic" power (note a deliberate variation on the word "Demon"; unclear). The phrase "Ur-vile" is also used.

I however have little interest in the origins. There are two matters of much more practical concern. The first is the ability to construct lesser versions of these golems, following notes from the Lich's. Materials are costly, and the result is somewhat useful but considering the expense there is no great value compared to hunting and capturing fodder as needed. I will continue to see if I can improve upon the formula.

A possible avenue to explore for that dovetails with the second matter, and that is the ability to control the original golem. The Lich had some ideas in that matter although his notes don't say if he had the opportunity to try them, or if they were successful.

My plan, therefore, is to lure the golem into a test environment which will allow me to observe the creature, perhaps even obtaining a sample. This might help with the creation of my own golems. And it will also give me an opportunity to try the Oblivion King's controlling method, which would of course render my plans much simpler.
My spies tell me that the group that slayed the Oblivion King and controls the golem creature has moved to a previously unoccupied territory in the Five Kingdoms that just serendipitously enough houses a major opening to the Underdark. I can therefore clear out a suitable area, acquire various fodder to populate it with, and bring the group in for the experiment.

The Lich's research states and my spies confirm that the golem follows a member of the group but that she is unable to actually control it. However, she and the remainder of the group is quite powerful, evidenced by their disposal of the Lich. Best case scenario, the group will die and I will have full access to the original golem. But I shan't hope for that; more likely I will simply get the opportunity to observe and improve upon the Lich's schemes in this area.