Order // Chaos — ruling 1

To cast a split card, choose one of its halves to cast. There's no way to cast both halves of this split card.

Order // Chaos — ruling 2

Split cards have two card faces on a single card. The characteristics of the half you didn't cast are ignored while the spell is on the stack.

Order // Chaos — ruling 3

Each split card is a single card. For example, if you discard a split card, you've discarded one card, not two. If an effect counts the number of sorcery cards in your graveyard, Assault // Battery counts once, not twice.

Order // Chaos — ruling 4

Each split card has two names. If an effect instructs you to choose a card name, you may choose one of those names, but not both.

Order // Chaos — ruling 5

A split card's characteristics are a combination of its two halves while it is not on the stack. For example, Assault // Battery has a mana value of 5 while it is in your library. If an effect allows you to search your library for a card with mana value 4 or less, you can't find Assault // Battery.

Order // Chaos — ruling 6

If an effect allows you to cast a spell with certain characteristics, consider only the characteristics of the half you're casting. For example, if an effect allows you to cast a sorcery spell with mana value 2 or less from among cards in your graveyard, you could cast Assault this way, but not Battery.

Order // Chaos — ruling 7

If you copy a spell that's half of a split card, the copy copies that same half. For example, if you copy Assault, the copy is also Assault, not Battery.

Order // Chaos — ruling 8

Chaos will stop any creature from being declared as a blocker that turn, including ones that weren't on the battlefield as Chaos resolved.

Order // Chaos : règles, fonctionnement et interactions (MTG)

Order // Chaos is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Exile target attacking creature. Creatures can't block this turn.

How it works : Order // Chaos

Original English text — Wizards of the Coast / Scryfall

#1December 8, 2022· Wizards of the Coast
To cast a split card, choose one of its halves to cast. There's no way to cast both halves of this split card.
No other card is named in this ruling.
#2December 8, 2022· Wizards of the Coast
Split cards have two card faces on a single card. The characteristics of the half you didn't cast are ignored while the spell is on the stack.
No other card is named in this ruling.
#3December 8, 2022· Wizards of the Coast
Each split card is a single card. For example, if you discard a split card, you've discarded one card, not two. If an effect counts the number of sorcery cards in your graveyard, Assault // Battery counts once, not twice.
No other card is named in this ruling.
#4December 8, 2022· Wizards of the Coast
Each split card has two names. If an effect instructs you to choose a card name, you may choose one of those names, but not both.
No other card is named in this ruling.
#5December 8, 2022· Wizards of the Coast
A split card's characteristics are a combination of its two halves while it is not on the stack. For example, Assault // Battery has a mana value of 5 while it is in your library. If an effect allows you to search your library for a card with mana value 4 or less, you can't find Assault // Battery.
No other card is named in this ruling.
#6December 8, 2022· Wizards of the Coast
If an effect allows you to cast a spell with certain characteristics, consider only the characteristics of the half you're casting. For example, if an effect allows you to cast a sorcery spell with mana value 2 or less from among cards in your graveyard, you could cast Assault this way, but not Battery.
No other card is named in this ruling.
#7December 8, 2022· Wizards of the Coast
If you copy a spell that's half of a split card, the copy copies that same half. For example, if you copy Assault, the copy is also Assault, not Battery.
No other card is named in this ruling.
#8December 8, 2022· Wizards of the Coast
Chaos will stop any creature from being declared as a blocker that turn, including ones that weren't on the battlefield as Chaos resolved.
No other card is named in this ruling.
#9December 8, 2022· Wizards of the Coast
Casting Chaos after blockers have been declared won't cause any of those blocks to be undone.
No other card is named in this ruling.