The Rulebook - Devilgram
"Mammon! I can't belie..."
Lucifer claims that the rules have changed, as he decided to change them according to the situation. Mammon complains about the situation in their family and Lucifer being full of himself. A flashback happens: Mammon reports to Lucifer that he checked up on their brothers and those who had nightmares due to the fall are now able to rest well and will heal in time, but he's still worried about the twins. He reassures a doubtful Lucifer that he doesn't regret following him, and reminds Lucifer that others rely on him and his strength, so he tells Lucifer to be proud to the point that people consider him full of himself. Back to the present, he hangs Mammon on the chandelier and tells him that it's his own fault that he's so full of himself.