Part of a cycle that features the almost-as-broken Gaea's Cradle and somehow the hilariously unbroken Shivan Gorge, Tolarian Academy taps to make a mana for each artifact you control, which led to decks that would dump their entire hand of cheap artifacts, make a ton of mana by tapping and maybe untapping Tolarian Academy, and then use big card-draw spells like Windfall and Stroke of Genius to refill before eventually milling the opponent out with Stroke of Genius, potentially all on Turn 1
These include the normal summon/set of one monster (in face-up attack position or face-down defense position respectively), any special summons you are allowed, the activation/setting of spells and traps, and changing battle positions of your monsters, including flip-summoning facedown defending monsters into the face-up attack position
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While it is a fairly expensive card, its effect and color made it a must-have for Green decks