Abysscraft, known as Nightmare in Japan, is a class in Shadowverse: Worlds Beyond and Shadowverse: Evolve. It combines Shadowcraft and Bloodcraft from Shadowverse and as such features a playstyle and mechanics drawing from both classes.
In SVE, these include followers with abilities such as Necrocharge, which activate once you have a certain number of cards in your cemetery, and Sanguine, which activate if your leader's defense has been reduced during the current turn.