If you would write what cards you have, i would be glad to help you with building a Nightmare deck.
first piece of advice: Sargh and Erzsebeth are two cheap cards that will help you win rounds without outpilling your opponent, something you need in a Nightmare deck, as your power is generally not that great.
Mojo is a good supplement, to begin with, because your lack of dammage forces you to considder lifegain abilities, later however you would do well to find a card with higher power to replace her.
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