When the initial chain is formed in combat with both attacker and defender triggers, who gets priority first to play reactions - the attacker (who has focus) or the defender (who controls the topmost chain item)?

Ruling: The attacker retains priority after the initial chain is formed. When items are finalized to the chain, priority does not pass (per rule 333.1.a), so the attacker who gained focus and priority before the initial chain was populated keeps priority.

Sequence:

• Attacker gains focus and priority
• Initial chain is populated with both attacker and defender triggers
• Finalizing items to the chain does not pass priority
• Attacker retains priority and has first opportunity to play reactions

Nuances:

• The rule about the controller of the topmost chain item gaining priority (333.1.c.3) only applies when certain item types (add abilities, units, gear) resolve, not when items are finalized to the chain
• This is acknowledged as unclear in the current rules formatting and may be clarified in future CRD patches
• In practice, going second with reactions is often advantageous since you can see what your opponent does first