Demonomancy is closely allied to Goetia and necromancy. Basically, one summons a demon and asks it questions about the future. It seems that demons are required to tell the truth at all times, whether they want to or not, however, can you trust a demon to tell the whole truth? No, not really. Omission is not lying and therefore, demanding to know the winning the lottery numbers doesn't mean that the demon will tell you that you'll lose the ticket before cashing it. Or get hit by a bus on the way to get it cashed. Really, you're better off not knowing those numbers.