pokemon 151 japanese expensive cards Mewtwo (Art Rare) - SV2a: Card [Japanese] Pokemon Card 151" Secret Rare

While each spell you cast technically only nets half a spell, counter doublers or cards like Kami of Celebration that distribute counters for casting spells from exile make it a one-to-one balance

If that half has any abilities that trigger "when you unlock this door," those abilities trigger at that time

While having a couple of newer versions (Thalia and The Gitrog Monster & The Gitrog, Ravenous Ride), I have this one as the best one

Tempest Djinn

For example, if a creature dies during combat on your turn and you cast Muster the Departed during your second main phase, its last ability will trigger at the beginning of your end step