The armor of Achilles, which had covered the body of Patroklos and which is now about to cover the body of Hector, is not just ‘immortal’: it is ‘immortalizing’. It will make you immortal unless it stops covering you, as when this armor falls off the body of Patroklos in the course of his death scene as narrated in Iliad 16. On the semantics of ambroto- as ‘immortalizing’, see the comment on I.16.670.