If I pass focus without using an action spell while moving into combat, and my opponent activates Hextech Ray, does it resolve first or does focus pass back to me so I can use an action spell like Cleave before resolution?

Ruling: Hextech Ray resolves first. You cannot play an action spell while there are items on the chain. After the chain resolves completely, you regain focus and can then play an action spell like Cleave to start a new chain.

Sequence:

• Opponent plays Hextech Ray (action spell)
• You may only respond with a reaction spell, not another action spell
• If you don't respond, Hextech Ray resolves
• Chain completes
• You regain focus and may now play an action spell (like Cleave) to start a new chain

Nuances:

• You gain Priority (not Focus) when responding to spells on the chain
• Action spells can only be played when the chain is empty
• Chain resolves in "Last In, First Out" order