Batching

Batching is R&D slang term used for the action of taking various (preexisting) game components and then connecting them into a larger group with a new word. Mark Rosewater sees batching as a design tool with interesting design space.

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 * Historic was the first example of batching. It collectively refers to artifacts, anything with the legendary supertype, and Sagas. The keyword refers to historic largely in the context of cast spells or cards off the battlefield, though three refer to historic permanents.
 * Party is a mechanic that batches Cleric, Rogue, Warrior, and Wizard. The keyword only refers to creatures controlled, and all designs use it to return a numerical value.

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 * Decorated cards include premiums, promos and cards with alternate art or alternate card frames.

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 * Mystical was considered for Throne of Eldraine. It would batch artifacts, enchantments, and Faeries.