Tournament rule 602.4.b.8.a
Additionally, players may change their domain identity, Rune Deck, Legend, and Chosen Champion while sideboarding as long as the resulting deck still meets 602.4.b.3-602.4.b.5.
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Additionally, players may change their domain identity, Rune Deck, Legend, and Chosen Champion while sideboarding as long as the resulting deck still meets 602.4.b.3-602.4.b.5.