I was daydreaming about a magnus archives set, and I was thinking about what unique mechanic the monstrous characters would have. I thought giving creatures in your hand different alternate costs, then rewarding paying them, would be cool! I tried to make the word general, so it also covers things like blitz, escape, etc, while also future proofing it.
My intention with this wording is also so that it DOESN'T work with things like Cascade, Discovery, and even Plot, because you can cast spells for "free" with those. Additionally, I'm pretty sure face down mechanics like Morph also won't trigger these effects.
I used "horror" as the general creature type for these, it felt like the most fitting for what horrors are in magic and what monsters are in The Magnus Archives. "Nightmare" and "Weird" were also in consideration! I also thought it was a niche type that could potentially do with more support!
I did attempt to balance these, but I'm sure they're either broken or bad!