Demons are often big creatures with high power, so being able to use them to blast an opponent's creature off the board or even go straight for their face gives you a way to either force the life loss that Abaddon so desperately wants, or simply bring everyone else down to your life total
For example, during the prerelease season of this set, the #1 Dwarven Ring was found, and sold for $13,000
You can insert any card name here you'd like, Mickey can play it for as low as two ink
As mentioned before, Blue decks promote card-drawing while Black decks promote lifesteal and "death and taxes" playstyles
If you cant readily sacrifice to this, try to play only one copy, as paying 5 for this is ideally more of a fallback