"Leon...? What happened to you?" Lucifer asked, his face paler than normal. He was standing in the infirmary, his eyes sad as he watched the former angel... the former light of the Celestial Realm... after Lucifer himself fell. Silence hung in the air for a moment before he spoke again. "You were never like this before..." the demon shook his head slowly, frowning as he began what sounded like a sentimental speech.
"You used to be so... happy... so bright... I can't believe this happened..." he wasn't certain if Leon was even conscious, but still, he continued. "Now you know how most angels are... how cruel... but when I met you... you were the first angel I ever met to be kind, with no trace of cruelty," his voice cracked slightly at the end of his sentence: "just like your father. But then he changed. For the worse. All sense of kindness drained out him. He wasn't the same angel. And now... I don't even know who you are, Leon!
"Maybe I always knew this would happen. Every angel that comes to the Devildom seems instantly corrupted. Ruined. And that's what I did to you. Maybe... maybe this isn't your fault. Maybe it was me who caused this." Lucifer fell silent, staring down at his ruined gloves, burned by fire - fire that wreathed Leon as he fell down, down, down into the pits of the reality itself - the Devildom.
The former angel let out a broken laugh, staring at the blank wall as he shook his head. "I'm talking to you, and you can't hear a word I'm saying. What I mean, is that I'll always be on your side, Leon. Whatever happens, I'll protect you. I won't let myself make the same mistake twice."
{Sorry it's so long! I just had a random burst of inspiration, and you said you wanted an interaction from a Lucifer account.}