OK, the exact instant the game has registered the death?
Code:
monitor_conditions not I_WorldwideAncillaryExists Patriarch_Roman
and I_CompareCounter deadevent != 1
historic_event patriarch_dead
set_counter deadevent 1
end_monitor
Assign the anc at character turn end and then:
Code:
monitor_event FactionTurnStart FactionIsLocal
and I_WorldwideAncillaryExists Patriarch_Roman
and I_CompareCounter deadevent == 1
set_counter deadevent 0
end_monitor
I guess that might work. At least you'd see in the log exactly when the character's anc vanished.