Nightmare

Nightmare is a rare Silent skill that chooses a card and adds 3 copies of it to your hand at the start of your next turn, costing 3 Energy and Exhausting. This triples the presence of any card in your deck for the following turn — choosing Catalyst delivers three Catalysts, choosing Deadly Poison delivers three more applications, or choosing a power like Noxious Fumes means playing it three times.

Nightmare's strength comes from amplifying already-powerful cards. The most common targets are Catalyst (exponential Poison scaling), Well-Laid Plans (stacking trap cards), or high-value rare skills. It requires spending an entire turn's energy on setup, so it needs to pay off on the following turn. In a Poison deck, Nightmare into Catalyst can produce a 27x Poison multiplier (three Catalysts each tripling). Upgraded, it no longer Exhausts, allowing Nightmare to cycle back and be used again across multiple turns.