In that split-second moment, the two reapers and one human conspirator came to an agreement. The hostilities would end, and Anubro would lend his considerable powers to aid this unholy union of man and reaper as they go to war with the rest of the Abyss. In exchange, should Morgana and Leo fail or falter in their endeavor then Anubro would devour their souls himself and add their power to his own. It was basically a Reaper's Pact for reapers.
As a concession to raising the white flag, Anubro made Morgana and Leo promise not to punish the dissenters he'd coerced into rebel against Adventour. At most, they were allowed to sanction them with a heavy soul stone fine, and the possibility of earning more money was the only thing that made Morgana agree not to fry their souls over a fire pit.
