Can you play Zhonya's from hidden in response to Faefolk's deathknell trigger after combat to save the Zhonya's (letting Faefolk die), and does this work outside of combat (e.g., if Falling Star kills Faefolk)?

Ruling: You can play Zhonya's from hidden in response to a deathknell trigger that occurs during combat to save the Zhonya's. However, this does NOT work outside of combat - if a spell like Falling Star kills Faefolk, you must use Zhonya's before the unit dies or it will be trashed.

Sequence:

• During combat cleanup, deathknell triggers are added as pending items
• The unit dies and is placed in trash
• The deathknell trigger is finalized to the chain
• At this point, the battlefield is still contested (contested status is not removed until after the chain resolves)
• Players can respond to the chain with priority, including playing hidden cards like Zhonya's
• Because the battlefield is still contested, hidden cards are not trashed yet
• After the chain resolves, contested status is cleared and control is established

Nuances:

• This interaction only works during combat because contested status keeps you in control of the battlefield even after your unit dies
• Outside of combat, there is no contested status, so hidden cards are trashed immediately when you lose control
• If you play a unit (not just Zhonya's) in response to the combat deathknell, a new combat will be staged with the same attacker and defender designations
• This interaction is considered unintuitive and may be changed in future rules updates, but it is how the current rules work as of version 1.2