For those unfamiliar with the term, a top-down set refers to a design where you start with the flavor and build the mechanical structure around that flavor
They enhance the look and make an impression that lasts
However, many scalpers want to keep sets like this sealed so they can flip them on eBay for triple the price
When triggered, the field parts and graveyard are unlocked and the central piece rotates the graveyard and field into play position
Once per turn, during your Main Phase: You can Fusion Summon 1 Spellcaster Fusion Monster from your Extra Deck, using monsters from your hand, field, and/or "Prince of Fairies" your opponent controls as material
Its a unique combination of numbers thatd never been done before in quite that way and was one of a few cards that turned green from the worst color in Battle for Zendikar into one of the stronger colors in Oath of the Gatewatch