I guess I can answer another one now.
Eol was known as the dark Elf. He took Aredhel, Turgon's sister, as his wife.
They had a son, Maeglin. Aredhel and Maeglin were essentially Eol's prisoners. When they tried to escape and return to Gondolin, he followed them and was captured by the Noldor of Gondolin. When he was brought before Turgon, he was given the option of living his life out in peace in Gondolin, but he took out a spear and threw it at Maeglin. Aredhel leapt in the way, and was pierced by the spear.
The wound did not seem to be serious, but the spear was poisoned, and Aredhel sickened and died overnight. Therefore, the following day, Eol was taken to the top of the battlements and cast over the side, to his death.
Small correction to the previous answer if I may. It was Turgon who left the arms for Tuor, at Ulmo's direction.
Edit: It appears that not one, but two people beat me to it.
Woohoo!