Source: The Silm
Disclaimer: Tolkien told this tale first.
My brother heard Elwing’s Silmaril was at the Havens of Sirion, but guilt for slaying our kin stayed his hand... at first. The oath’s torment was not something we could dispel. We marched again, though there were changes amongst our people. Some stood aside from battle, some rebelled, fought against us – and were slain. But we won no victory.
My twin brothers died there; Elvish blood stained my blade... I ravaged, destroyed... until I discovered Earendil’s twin sons...
Some might commend it as charity that I cherished them... but vainly seeking redemption for terrible wrongs...? That is no selfless act.