Mouths of Sirion with the Silmaril. 509 - Maeglin captured by Morgoth's spies. 510 - Gondolin is betrayed by Maeglin and sacked; Glorfindel slays a Balrog in the Echoriath , Ecthelion slays Gothmog , both of them killed as well. Death of Turgon . Tuor and Idril escape. 511 - Tuor