If all defending units die in combat and one has Deathknell, can the defender reveal their hidden unit in response to the Deathknell trigger before losing control of the battlefield?

Ruling: This is an unresolved rules ambiguity in CRD 1.1 with no official answer. A head judge would need to decide between multiple interpretations.

Possible Rulings:

• Option 1 (RAW): The defender can reveal the hidden unit in response to Deathknell since they still control the battlefield at that moment, potentially leading to a second combat
• Option 2 (RAI): The battlefield's contested status should be removed during cleanup before Deathknell triggers, meaning the hidden card is already discarded and cannot be played
• Option 3: Playing the hidden unit would create an illegal game state (two players controlling the same battlefield simultaneously), so the unit cannot be played

Nuances:

• This ambiguity only exists under CRD 1.1 rules; prior versions handled this differently
• The issue stems from new rules about maintaining control while a battlefield is contested
• Attacker recall would not happen again regardless, as that step has already passed when Deathknell triggers
• No major tournaments have occurred under CRD 1.1 to establish precedent