You long ago stopped caring about the differences between you. Her head of hair is beautiful and soft to the touch, but your lack thereof makes it all the easier for her to plant tender, gentle kisses along your skull. Her umber skin complements your green hues in a way that reminds you of foliage and timber and life, the beauty of Earthen nature which neither of you ever knew outside of photographs and movies. Your clawed hands and feet dwarf her softer appendages and over the years you've grown to tower over her, but she was always quick to point out that that didn't make her weak in comparison -- at first, that is.
For the first several decades of your life with Roxy, you cherished the differences between you.
Now you wish you could erase them.
When she holds your hand in hers, her papery grip is frail.
When she says "I love you," you can hear her voice trembling, weighed down by the many years.
When she kisses you, it's as perfect as it ever was, full of love and passion. But when she pulls away you see again the wrinkles adorning her skin, the exhaustion in her eyes, the grey tint to her once vibrantly pink hair.
She can no longer wield most guns or focus on the lines of code that once filled her with such passion; when she's too tired to put her teeth in she can no longer eat most foods; and some days, it seems like she spends more time asleep than awake.
You would gladly grant her half of the millennia allotted to you if you could. But no matter how you wish, there's no altering human physiology.
Help me, you plead to something or someone. To the gods of the Void, who don't give half a fuck that the wielder of their element is succumbing to decay. To Skaia, whose light dimmed longer ago than you care to think, and who could not save her anyway. To the long-vanquished half of you who reigned over Time. But you're not him; Space is your domain, and there's nothing Space can do but separate you from her as Time is doing now.
You can do nothing but watch helplessly as the one you love more than anything or anyone else is gradually swallowed by the years.
She fades away, and you remain.