(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)
Moldering Gym
When you unlock this door, search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
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Weight Room
When you unlock this door, manifest dread, then put three +1/+1 counters on that creature.