Summary: Perhaps it is an old prejudice which also leads Thranduil to disapprove of Tauriel when it comes to Legolas. Just a short piece from Thranduil's POV, First Age allusions abound. Enjoy!
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Red Like Blood
Not many Elves are born with red hair. It is an unusual trait amongst all kindreds, though I have encountered it most frequently during the past age while ruling over the Silvan Elves of the Greenwood. I have never known any of my own people, the Sindar, to have red hair.
One of my subjects, the young Silvan maiden Tauriel, boasts an impressive head of red hair. For several centuries now, she has been a close companion in arms to my only son, Legolas; but with a father's eyes, I can see their friendship deepening into something more. Certainly from my son's perspective, possibly from hers.
But I cannot allow this; though she has proven herself brave and faithful, a common Silvan Elf has no business being wed to a prince of the Eldar. Although, granted, Elves greater than my Legolas have married even farther beneath their stature in the name of love. Perhaps I should be grateful that Tauriel is at least an Elf.
But no. If I am honest, there is more to it than this, more that I could never voice aloud to another soul. Perhaps Celeborn would understand, even if he would never admit his prejudice openly. There are times, rare but persistent, when a glimpse of Tauriel's red hair in the corner of my eye will haunt me, awaken memories deep inside that ought never to have seen the light of conscious thought again.
Memories of even brighter red hair on a broader, taller figure. Hair red like blood staining the winter snow, slick on the floor of the Thousand Caves. Red like the blood on Sirion's banks. Red hair whipping in the fury of battle while an expertly-slit throat silences the screams.
How the horror grips me when those moments come, and I am trapped in grief anew, no matter what transpires around me in the present. I can only wonder what Legolas must think of me in those times, for I know he sees my weakness more clearly than the rest. He sees, but he will never understand, not even if I were to tell him all.
Truly, my son is blessed in his ignorance, innocent despite his many centuries as a warrior. It is for his sake that I conceal from him certain things that are long past; it is for my own sake, in part, that I warn Tauriel to distance herself from him.
Nay. I will not see it come into the bloodline of Oropher, into the royalty of the Sindar. I will not allow the chance that my own grandchildren might be born with hair the color of freshly spilt blood – hair the color of fire.
They tell me fire claimed him long ago; if only fire could so thoroughly end the memory of him as well.