Orcs... were elves?

[Formendacil]

Originally Posted by Lalwendë

I also like the idea that Orcs are bred from several races, as it does allow for the many varieties. But if they were descended from Elves it also makes for a lot of interesting possibilities - e.g. could the Elvish nature be entirely taken form them? Were they immortal? What happened when they died? etc.

Only Orks with pureblooded Elven ancestry (tormented by Morgoth or no) would be immortal. Tolkien stated, with regards to Half-Elves, that they were inherently mortal, sharing the Gift of Men. Only those to whom the Choice was given: Eärendil, Elwing, Elrond, and Elros had a choice. The default setting was mortality, and so Dior, Elured, and Elurin died indeed and are gone beyond the circles of the World. It can also be taken as an explanation for why the Elven-choosing next generation of the family: Elladan, Elrohir, and Arwen, were given a Choice, whereas the Sons of Elros were stuck with their father's lot.

It therefore follows that part-Elf Orks would not have been Immortal. They would likely have inherited many other Elvish traits and there would certainly have been great enmity between Elf and Ork, but unless an Ork was of pure "Elvish" ancestry, he (or she) would not have been immortal within the circles of the world.