While the name or title of this topic is not officially recognised in-game, the information contained on this page is still considered to be canon and is based on official sources.
An intruder destroys Oaknock's machine during a cutscene in The Eyes of Glouphrie. He uses an illusion device to become translucent, and looks very similar to Glough.
If a player has started Monkey Madness I, they will remark that Karam used a similar type of magic to make himself invisible.