Biomechanical elves, feat. Maglor and Galadriel! Because you don’t live for ~5000 years on one hröa without needing some maintenance.
Additional thoughts below the cut!
Okay, here’s the logic:
1.) Elves live forever unless killed
2.) Elves cannot grow back limbs like starfish (c.f. maedhros)
3.) Elves, due to their preternatural endurance, are very likely to survive having limbs hacked off (c.f. maedhros again)
4.) Elves, especially in the First and Second Ages, spend a lot of time trying to stab each other and/or fighting things that want to rip them to shreds (orcs, werewolves, etc.)
Rinse and repeat long enough, and by the Third Age, most older elves would have several serious permanent injuries. Conveniently, elves also have a cultural predilection for a.) the healing arts and b.) magic smithery, which gives us an excellent fast-track to automail-type fantasy prostheses.
I drew Maglor and Galadriel, who have decent odds of rocking the most metal-per-hröa by the time of LotR.
Maglor has a vocal prosthesis (maybe for smoke inhalation during the War of Wrath, specially calibrated for singing-laments-upon-the-shore purposes); a cranial implant/helm (I like to think Elwing chucked something heavy at him); a gauntlet (to restore fine motor control to his Silmaril-chucking and harp-playing hand), and a prosthetic leg.
Galadriel has several implants and a prosthetic arm. The crown-with-circuitry is a helm designed to offset migraines (a common side effect of peering into things that are, once were, and have not yet come to pass.) It was made for her by Celeborn, who is her husband AND her mechanic, and is also why he gave her the nickname Galadriel.
For obvious reasons, prostheses are wayyyy more common in Middle Earth than Valinor! There are some prosthetic and mobility aid craftspeople in Aman who make tools for elves who were injured on the Great Journey back in the Years of the Trees (or born with conditions that necessitated it!) However, I think the technology probably advanced a whole lot faster in the East, so skilled mechanics arriving in Valinor would be warmly welcomed. I drew the prostheses with exposed metal for the Aesthetics, but I do think elves would develop some kind of grippy skin-like surface for functionality.
