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>If you successfully cast a Normal Spell or Item Card, it is removed from your deck for the duration of the current Duel, unless it is reshuffled.
>At higher levels, a Spell to Reshuffle your deck is available. It can be useful if you are using a small deck, or are drawing many ineffective cards. Once all your cards have been played or discarded, your Wizard will be left helpless, unless a Reshuffle is performed. Note that each Reshuffle in your deck can only be used once per Duel.
Oh, guess I was wrong about having a feeling that they somehow cycled back automatically. Strange that I hadn't even noticed the deck diminish even while having like a tiny-ass deck. Although in my defence, playing myth the summoned minion casts half of your spells during a combat so it's harder to keep track of every single copy of a card. Still, minimum viable deck size is gonna be best for consistency.