How we cite our quotes: (Story.Chapter.Paragraph)
Quote #7
But Time, having initially gone for the throat, was now setting out to complete the job. The boiling interface between decaying magic and ascendant entropy roared down the hill and overtook the galloping horse, whose riders, being themselves creatures of Time, completely failed to notice it. (2.10.129)
Okay, so maybe there is a power greater than the Lady's: entropy. Given enough time, even Bel-Shamharoth will fall victim.
Quote #8
Liessa bends her mind to the task of full visualization; above her in the musty air the dragons become fully visible, bronze scales dully reflecting the sunbeam shafts. Her mind throbs, but now that the Power is flowing fully she can, with barely a waver of concentration, think of other things. (3.7.2)
Imagination is also a super powerful force on the Disc, thanks to the fact that it exists in the physical world as octarine. This allows imagination to take physical shape in the form of magic and dragons. Super cool—depending on whose imagination we're talking about here.
Quote #9
"You have the Power!" "All I did was think of it." "That's what the Power is! Have I already told you that I am Greicha the First? Or is that next? I'm sorry, but I haven't had too much experience of transcendence. Anyway, yes—the Power. It summons dragons, you know." (3.13.60-62)
The other great thing about imagination being a power in the world is that no one has to be trained to use it. Twoflower was trained to not be imaginative, but his power of imagination is so powerful that he creates one of the best dragons ever.