You're right though, it makes sense that Mammon might do something like that. Mammon adores MC and he's going to be devastated even thinking about losing them, up until he and his brothers find a way to prevent it. Because he will not lose them, he can't–

For demons, the passage of time means just that. Days turn into months turn into years turn into centuries, and not much changes. Demons take for granted that Solomon is a rare exception, not the norm, when it comes to aging and mortality. Most humans talk about time differently than demons, too—they realize it's a rare, finite commodity they have to make the best of.

Take Mammon's precious human, for example. He starts to notice little groans or hisses of discomfort they make when their body aches in ways it never used to. They scrutinize their appearance in the mirror more often, and realize their skin's not as firm—and is that a grey hair?!

Maybe Asmo notices too, those times when he scrolls through his Devilgram feed to look back on fond memories with you. He sees you all the time, but looking at photos from a year ago? Five years ago? He can see how much you've changed.

If the demons haven't figured out a way to address their beloved human's mortality already, something is going to remind them that they're running out of time.

[Mammon x gn!Reader, 0.6k words, sfw. Content warnings: references to death/mortality, grieving, angst.]

Mammon put on the cheesy-lookin’ human world movie because it was long after midnight and sleep eluded him. He figured if it was as dumb as it looked, he might finally doze off.

By the time the end credits start rolling, he's a blubbering mess.

He’s always cracking jokes and making sarcastic commentary during bad movies. Ain’t that the whole point of watching ‘em, to have a good laugh?

But sometimes movies caught him off-guard, like the one tonight. Those were usually the films you picked, the ones you promised he would enjoy and you would accept the consequences if you were wrong.

(Maybe you make everything so much better just by being there with him.)

Mammon doesn’t like to think about the possibility of you not being there anymore. He already has to deal with your visits to other realms which is annoying enough, but he can deal with that. It's the thought of you being gone forever, the thread of your human life inevitably cut when you grow old, or if something happens to you—

He hates thinking about it. It’s like a black hole inside him that traps his heart in a vicegrip and makes it impossible for him to breathe. He takes for granted that most humans aren’t like Solomon—you won’t be around forever, and he tries so desperately not to think about it because it kills him inside.

He tries to do what everyone else does: carrying on and basking in the warmth of your very existence without considering what comes next. If the others worry about the day when you suddenly won’t be there anymore, no one else says anything.

(But sometimes Asmo frowns when you peer at your reflection in the mirror and joke about the little wrinkles you’ve developed, and Beel shoves more food onto your plate when he thinks you’re not eating enough, and Levi complains that you’re too tired to pull all-nighters with him like you used to.)

He wipes his eyes and curses this damn movie about the lovey-dovey human couple growing old together, how they lived together and loved together and eventually died together. It should be romantic, but it fills him with dread.

Mammon looks down at the pact mark etched on his skin. One day you’ll disappear, and your pact mark will too. He won’t be able to chase after you anymore to keep reminding you that he’s yours, and you’re his.

He rushes across the house in a panic and ends up outside your bedroom. He can hear you snoring softly on the other side, but the familiar sound is a small comfort. He cracks the door open, and the light from the hallway spills across a familiar lump underneath your blankets. He doesn’t mean to wake you when he slips between your covers and melts into the warmth of your body as he wraps himself around you.

You peer at him sleepily, eyes half-lidded and unfocused. “Wazza’matter?” you mumble with a yawn. You wrap an arm around his waist and snuggle closer to his chest. “Y’okay?”

Tears roll down his cheek and he swallows around the lump in his throat. He doesn’t answer right away—not until he suppresses the urge to sob uncontrollably, like he just did in his room.

“Just couldn’t sleep,” he whispers, and you’re too tired to notice the way his voice cracks.

“M'kay. G’night, Mammon,” you murmur as your breathing slows and your body relaxes in his arms.

He holds you close and matches his breathing with yours. He strokes your back and bites his lip whenever a new wave of tears fall from his eyes and drip onto your pillow.

He knows by morning the stains will be dry, the evidence of his despair washed away by time, just like you will be one day.

He's so exhausted but his heart is heavy. He doesn’t sleep.