Rule 486.6.a

This format may be played as best of 5. In such a case, during games 4 and 5 of the match players may present a battlefield that has been removed from the game.

• 486.6.a.1 Players may only re-use a battlefield in this way if they have already presented each of their battlefields at least…
• 486.6.a.2 Players may not present a battlefield more than twice in a match when re-using battlefields in this way.

Official Core Rules