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What would a ghost who took on a human lover do when they eventually die
As the passage of time starts to overtake your lover, you and your other partner stay the same. Their lustrous hair begins to gray while yours remains the same ethereal white. Your partner's strength deteriorates as their body ages while you're as spry as ever.
For once in your afterlife you feel helpless as all you can do is stay by their side and help make their final years just a little easier.
Technus doing tech repairs on all of the appliances, siphoning electricity from the power grid so their human lover doesn't have to worry about paying the power bill anymore. If they need health related devices like a pacemaker Technus makes damn sure there's no fault in it.
Skulker piling his prized pelts that once adorned his walls onto their sleeping body, wanting them to be warm and comfortable. Skulker going off on hunt after hunt of rare creatures or artifacts, anything that might delay the inevitable.
Neither know how to process the fact that their human will pass away. Both are no strangers to death, Skulker has killed many a creature after all. It's different when it's someone you care so much about.
They never thought they'd need to go through this in their afterlives, they were far past mortality after all as were all of the allies and friends they had made. With Skulker and Technus it was just a matter of how long they'd choose to be in each other's lives, there was no such concept of until death do us part. With the human...it was a grim reality they'd need to face sooner or later.
A selfish part of them hopes that when they pass they'll become a ghost. Their death would have just been a small footnote in their relationship. Hell, maybe their funeral would be a fun party to which they could invite all of the Ghost Zone. They could make showing their lover the ropes of the afterlife and life in the Ghost Zone a romantic endeavor! They could lovingly hold their hand as they worked them controlling and channeling their newfound abilities. A date night under the Ghost Zone's vast skies would be amazing as they taught them how to float and soar.
But they knew it wasn't likely. Ghosts formed normally after violent or extremely emotional deaths.
They hardly formed when one passes on in peace, surrounded by loved ones.