Who Am I?

[Eorl of Rohan]

Yes, it is Maedhros. Good guess, Loslote. You got the 1st, 2nd, 3rd, and 9th lines correct.

(4) My yet another betrayal was with faith repaid -> Fingon repaid Maedhros with faith by freeing him from the menacles
(5) Sought the end but was paid in loss -> He sought to die, and asked Fingon to kill him, but was paid by the loss of a hand
(6) Yet none shall claim in gratitude I was lacking -> He was grateful to Fingon despite him having cut off his hand
(7) My high hopes welded the children -> The children refer to the Firstborn (Elves), the Children of Men (Men), and the children of Ainu (Dwarves) -> They were welded in an alliance against the Dark Lord
(8) adopted and born and the beloved youngest -> Eru Illuvatar calls the dwarves his adopted children, while the Firstborn is his children by creation, and the beloved youngest is of course the children of Men, the Secondborn.
(10) My high delight set ablaze to grief and despair -> The Silmaril burned Maedhros' hand, which drove him to grief and despair.



PS. Loslote, if you have a bit of free time, come join us in our Shire Roleplay "Homeward Bound"~