Tournament rule 601.1.c
In competitions where a sideboard is allowed:
- 601.1.c.1 A player’s sideboard can include 10 or fewer cards.
- 601.1.c.2 A sideboard can consist only of valid Main Deck cards.
- 601.1.c.3 Limits on copies of named cards apply to the combination of main deck and sideboard.
- 601.1.c.4 A player may change their Chosen Champion to one from their sideboard or main deck that matches their Legend whenever…
- 601.1.c.5 See 403 for more information about sideboards.