In the book Gardens of the Moon we find that the Empress has sent Adjunct Lorn to awaken the Jaghut Tyrant in an effort to weaken Lord Anomander Rake. However we later find that she had a Lord of Galayn demon stored that was considered an equal to Anomander.
Is there any reason why they awoke the Jaghut Tyrant then? Other than to forward a bit of plot and have some sorcery battles go down? It seems the Tyrant was quite a big worry throughout the book, but then didn't really achieve much?
Just a note, I've only read the first book, so if this is revealed later, then it's understandable. But other than that it seems like a pointless plot device that's never used.