Interesting, because I have been spoiling Silenos, Turak Bugbear and Kanil Succubus now from lvl 28 to 34, and I have got 3 scrolls from Silenos and 1 from Bugbear, but all of them were drops, not spoil. And I have spoiled quite a few Kanil Succubi but no scrolls, even though they should have a better spoil rate.
So if it is still from spoil, then why do I get drops and no spoil on the scrolls?