Can players add reactions to the Initial Chain in between triggered abilities, or does the Initial Chain only contain triggered abilities?

Ruling: The Initial Chain only contains triggered abilities that are added in the specified order (attacker with focus, other players in turn order, then defender). However, once the Initial Chain is fully populated, it functions like any normal chain - the attacking player gets priority and all players can play reactions in turn order before anything resolves.

Sequence:

• Triggered abilities are added to the Initial Chain in order: player with focus, then other players without defender designation in turn order, then defender
• Once the Initial Chain is populated, the attacking player has priority
• Players can then play reactions following normal chain procedures (rule 333)
• Players cannot react to prevent triggers from going onto the chain initially

Nuances:

• You cannot chain block a trigger from going onto the Initial Chain
• Certain reactions can still impact triggered abilities (e.g., if a trigger requires a unit to be "here" when it resolves, removing that unit will cause the trigger to resolve but not produce its effect)
• Triggers once finalized will resolve unless their conditions are no longer met