The titular ability of Nightmare is his ability to appear in dreams, both prior to the sufferer experienced encountered him while in the flesh in the sort of ill omen or during the minds of survivors following a terrifying attack. He can change on the astral and ethereal planes. https://webcastlist.com/story21142370/how-much-you-need-to-expect-you-ll-pay-for-a-good-nightmare-mu-online-season-20