If a Ruined Rex dies in combat and its Deathknell kills the last remaining enemy unit, does that prevent scoring from that combat?

Ruling: Yes, the Deathknell can prevent scoring. Ruined Rex's Deathknell ability resolves during Combat Special Cleanup, which occurs before the Determine Combat Result step. If the Deathknell kills the last remaining enemy unit, leaving no units on either side, the combat ends with "No Result" and no player conquers or scores from that combat.

Sequence:

• Combat damage is dealt and lethal units (including Ruined Rex) are identified
• Ruined Rex's Deathknell triggers and is added to the chain as a pending item
• Lethal units are moved to trash
• Surviving units are healed
• The Deathknell trigger resolves via FEPR, potentially killing additional units
• Combat result is determined based on which units remain
• If neither player has units remaining, the result is "No Result" and no scoring occurs