Inside the Radiance Church…
The Liege of Death, having turned into a shadow, did not attack immediately. After finding out Francois' location, he backed off to a dark corner outside of the room while waiting for the shift of night to day and the moment when the gate of the cathedral was opened. That would be the moment when Francois was most relaxed and careless.
If he were to cast a spell right now, Francois could possibly sense danger and defense in time.
Since they were going to fight in a cathedral, he was not confident that he could defeat Francois when he hadn't recovered to his peak status yet.
Even though the cathedral was protected by the God of Truth, and lights were on all night, there was still darkness where the lights could not reach. The Liege of Death stood in it as if it had been melted into the darkness.