NOTE: These rules do not go into effect until the Diamond Rulebook has been released.  This includes the errata (unless it was issued previously)

Determining Who Starts
The player with the highest Starting Family Honor takes the first turn. If there is a tie, the players tied for highest should determine who goes first with a uniform, random method such as dicing off or flipping a coin.

Targeting
Some actions are targeted, meaning some aspect of them is aimed at a particular recipient. Targeted actions can sometimes have their aim directed elsewhere or be prohibited from directing their aim at certain cards. An action targets something if it uses the word "target" or if any player sometimes has to choose what it affects. If no player, under any circumstance, has to choose what gets affected, the action is not targeted. Example 1: Block Supply Lines sends home one attacking unit, bowed. Since there can be any number of attacking units, Block Supply Lines sometimes requires a choice. This means Block Supply Lines is targeted, even during battles where there is only one attacking unit and there is no real choice what to play it on. Example 2: Along the Coast at Midnight gives a trait to all of your Personalities and Followers. There is never a choice involved, so it is not targeted.

Targeting Bowed Personalities
The rule prohibiting targeting your own bowed Personalities with your own actions is being replaced by the simpler rule, "Bowed Personalities may not cast Spells. Bowed Personalities may not issue challenges unless caused by another player's effect."

Regions
All Regions will be "Singular". Each player may have only one copy of a Singular card in play at a time. Unlike Unique cards, a player may still include three copies of a Singular card in his deck, and a player may play a Singular card regardless of whether another player has a copy of that card in play. This rules change applies to all Regions ever printed.

Also, Regions are played more like Events: they enter play or get discarded immediately upon being revealed. Playing a Region will still be mandatory if it is legal and has no cost.

Seppuku
Courtiers will be able to commit seppuku like Samurai.

Errata

1,000 Years of Darkness
Gifts and Favors: You search your deck and face-down Provinces, and play the first Gifts and Favors you find. You lose the game if you find none. [MRP]

The Fall of Otosan Uchi
Private Dojo: You must bow Private Dojo to use the Reaction. [errata]

Tsuruchi Hiro: His Chi of 4 is a misprint. It should be 3. [MRP]

Vengeful Dead: The phrase "another player's card effect" should read, "another player's Ninja, Kolat, or Assassin action." [errata]

Heaven & Earth
Kanashimi: Replace "After a player draws a card outside his or her End Phase" with "After a player draws a card outside his End Phase due to his own card or Stronghold effect".

Noh Theater Troupe: This card is Singular. [errata]

Wholeness of Self: Its effect does not apply to focusing in duels. [errata].