Tournament rule 602.4.a.3

The domain identity of a sealed deck is any three domains, or any domain plus the domains of the deck’s Champion Legend.

• 602.4.a.3.a A sealed deck may have any Champion Unit that is included in its domain identity as its Chosen Champion, even one that…
• 602.4.a.3.b A sealed deck may contain any signature spells that are fully included in its domain identity, even if the deck does…

Official Tournament Rules