Secret Arcade // Dusty Parlor

The counter half reads like a standard enchantress payoff: whenever you cast an enchantment spell, one creature grows by that spell's mana value. Note that the trigger keys off the cast, not the resolution, so the counters land even if the spell itself is later countered, since the triggered ability resolves independently. On its own, that is a familiar incentive to jam enchantments and stack a single threat. The Secret Arcade half is what universalizes the tribe. Once it is unlocked, every nonland permanent you control and every permanent spell you cast is an enchantment in addition to its other types, so the counter trigger no longer cares whether you are casting an aura or an artifact, a planeswalker or a creature: they all now qualify. The Room framing is where the sequencing gets interesting, because the two doors unlock independently. Cast one half, and later, as a sorcery, you pay the mana cost of the locked door to unlock it rather than casting it again. That lets you get the counter engine online first, then flip the type-changing half on afterward and immediately begin feeding a stream of "enchantment" spells into a growing target. And because the counter trigger scales to mana value rather than a flat number, the payoff wants a curve topped high: one expensive permanent can dump a fistful of counters the turn it enters, no swarm required.