It is designed to hold four standard-sized cards, helping to preserve their condition while highlighting their importance in your collection
I frequently used Shared Summons to grab two of the combo pieces in my Yisan, the Wanderer Bard deck to go big on the following turn with Quirion Ranger and Scryb Ranger
In that sort of a role Remand is the vastly more desirable card, you want countermagic to deal with stuff cheaply and efficiently, you play card advantage spells to provide the late game inevitability and so you are just harming your own disruptive power by trying to combine the two into one overcost card
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This deck has destruction, discard, and mill, rapidly filling up your opponents graveyards
And that the informed Magician already knows all these things so you have to assume they're all going on from both sides of the table