Can players change decks between matches at low OPL/casual events like Nexus Nights, and can players agree to modify rules during their match?

Ruling: Players must use the same deck throughout an event at all OPL levels, even low OPL casual events, though this relies on a trust system since decks aren't registered. Players can agree to modifications or alternative outcomes (like RPS or joke decks), but either player or the judge can refuse or call it back to official rules at any time, which would result in losses for rule violations.

Sequence:

• Players can initially agree to play outside official rules (proxies, different decks, RPS, etc.)
• However, the opponent, judge, or event host can call it back to official rules at any point
• If unofficial elements violate official rules when called back, the violating player takes an instant loss
• The game can still be played out for fun only after the official loss is recorded

Nuances:

• Organizers can set custom prize structures however they want, but cannot change core gameplay rules and still call it an official event
• The lax side of low OPL only applies to allowing takebacks on misplays or mistriggers, not to deck construction or switching
• Pairing is only random in Round 1; subsequent rounds pair laterally by record (winners play winners), so casual decks will naturally face each other after early losses