Manahive

I assume you meant Dreamspoiler Witches. Equivalent cards (blue and black, with similar effects or synergy with instants) include:

• Nightsky Mimic (blue-black, reacts to casting blue or black spells)
• Faerie Tauntings (black, triggers on casting spirits or arcane, but similar “whenever” effect)
• Vendilion Clique (blue, faerie synergy, but hand disruption instead of -1/-1)
• Mistbind Clique (blue, faerie tribal synergy, tempo effect)

Reason: Few cards match the -1/-1-on-instant specifically, but many blue/black faerie cards offer similar synergy or triggered abilities.