If a Faefolk with a hidden Zhonya's dies in combat, can you respond to the Deathknell trigger with the hidden Zhonya's to save it for future use instead of using it on the Faefolk?

Ruling: Yes, when Faefolk dies in combat, the Deathknell trigger resolves on the chain after the special cleanup but before contested is cleared from the battlefield. At this point you still control the battlefield and can play the hidden Zhonya's in response to the Deathknell trigger, leaving it on the battlefield for future use.

Sequence:

• Combat damage is dealt and Faefolk is assigned lethal damage
• Special cleanup occurs (damage heals, attacking units recalled)
• Deathknell trigger is finalized in the cleanup immediately following the special cleanup
• Priority window opens with Deathknell on the chain
• You still control the battlefield (contested has not been cleared yet)
• You can play the hidden Zhonya's in response to save it
• After the chain resolves, contested is cleared from the battlefield

Nuances:

• This only works in the combat scenario with Deathknell. Without a Deathknell trigger, there is no window to play the Zhonya's if Faefolk dies to combat damage
• In the spell scenario (Icathian Rain), if you wait until the 3rd trigger resolves, Faefolk will be in the trash and cleanup will cause you to lose control of the battlefield, trashing the hidden card as well
• The combat cleanup substep is not itself a cleanup - the special cleanup invoked within it is the actual cleanup
• Clearing contested (440.1.b) is not part of the special cleanup, it occurs after combat cleanup plus any additional triggered cleanups