full art mew pokemon card EX #003 EXTENDED – Raycardza shuffle your deck. 2021 Pokemon Sword & Shield

You could target a bothersome creature in play or deal a little extra damage to your opponent

If it's a Siege, it will still be exiled when the last defense counter is removed from it, and its controller may still cast it transformed without paying its mana cost

Beyond just being good on its own, Nuka-Cola Vending Machine gets even better alongside Commander staples

Or, pay just one energy and make that Wurmcoil Engine an immediate threat

My best guess was that seven is one of the more common numbers for card games where you draw cards and perhaps it won out because it was what Richard Garfield thought people would assume to draw