2 PCs are dueling. Iaijutsu duel to the death. The duel is settled when one person is dead or dying.
So the 2 PCs fight and one person is struck with a severity 13 critical strike and suffers an Agonizing Death. Since they are now dying, the conditions of the duel is fulfilled.
However - Since the Dying condition doesn't specify that you cannot act, the PC decides to spend their 3 final rounds trying to take their opponent to the underworld with them.
Does the duel continue? Do we repeat phase 2, do another staredown and so on, until the dying character dies or manages to kill their opponent?
Or does it stop being a Duel and instead become a Skirmish between two people?