When does Deathknell trigger in a combat showdown, specifically regarding whether units like Kog'Maw heal before Deathknell triggers and whether Undercover Agent can play Chompers to a contested battlefield?

Ruling: The rules do not currently provide sufficient clarity for this interaction. There is no consensus answer.

Nuances:

• One interpretation suggests Deathknell triggers after cleanup, meaning units would heal before Deathknell effects resolve
• For contested battlefields, if Deathknell triggers after cleanup, the contested status would be cleared and neither player would have control, preventing units from being played there
• An alternative interpretation suggests Deathknell goes on the chain during cleanup but finalizes afterwards, potentially allowing Chompers to be played, followed by another cleanup and then control shift
• Playing Chompers to a contested battlefield creates a problem where two players would have control simultaneously, which violates the rules
• The current rules lack a definitive solution for these edge cases