Lyric discussion by Trinidadian 

Cover art for Third Immortal lyrics by Battlelore

Probably about the coming of the Istari from Valinor, Specifically Gandalf, as he is the only one who 'bows to the greater light.'

The best guess as to the song title I can think of is that the Istari were the 3rd immortals to come to Middle Earth, although that may be debatable. The Eldar are immortal, and also Melian who is a Maiar and presumably immortal came before also. Additionally, Morgoth as well as Sauron as well as other Maiar who are presumably immortal were there before the wizards. The Istari are thought to also be of the Maiar, so thinking is terms of 'classes' of immortals, there would be 3: Valar, Maiar and Eldar.

So there it is.

My Interpretation

Don't know what its about, but their were five Istari: Gandalf, Saruman, Radagast, and the two blue wizards.

Not Valid