In a Preconstructed deck event, can players add a third domain to their starter deck (like in Sealed format), or must they play the deck as-is from the box?

Ruling: Preconstructed events are meant to be played with the deck as it comes in the box. However, tournament organizers are free to modify this rule and allow upgrades or changes.

Nuances:

• The Tournament Rules indicate that Preconstructed Deck rules may override Limited Deck Construction rules (including Sealed's three-domain rule)
• Players cannot decide on their own to adjust their precon deck
• If the organizer specifies modifications are allowed (e.g., "everyone can use 4 packs to upgrade their precon"), then that becomes the event format
• Organizers must specify if any modifications to the base precon decks are permitted