Inmortales translates to "immortal". It's a strong, evocative word that carries significant weight, especially in a poetic context.
In this song, the narrator uses it to describe the enduring nature of his feelings, stating, "Por sentimientos que yo te juré inmortales" (For feelings that I swore to you were immortal). This emphasizes the depth and everlasting quality of his love, making it a powerful and memorable word choice.
This beautiful song by Cuban singer-songwriter Silvio Rodriguez is about a reluctant departure. The singer knows he's drifting away, even though he doesn't want to: "Aunque no quiero, veo que me alejo" [Although I don't want to, I see that I'm drifting away].
He leaves a message on the mirror and a postscript drawn in a cloud so his love won't forget him. He was followed by demons last night and didn't want to bring them to her door. He escaped them at sunrise and won't leave until she wakes up. He'll be a whisper and a shadow, leaving just two words that she'll know are his, a fading breath of immortal feelings he swore to her.