Another shot in the dark - Arnor? "Older brother" of Gondor that outlasted it, thus becoming greater. The ruins of Arnorian cities are filled with shadows, and I guess you could say that the people - ie rangers - are like shadows. The Witch-King (who was corrupted by Sauron) destroyed Arnor, and "weeping masters" would be the Chieftains grieving for the loss. The "eternal art" could be a lot of things with a stretch
... It might be that it's the Reunited Kingdom that is eternal because it outlasted and will yet outlast many a thing, and "master" would be Elendil...