Who or what is "El Ragna"?
Well, if you think about the lyrics, God(dess) would make sense.

The God(dess) that flies on the wind, making promises with destiny
The God(dess) that goes on the wind, with roaring wings

Also the wiki says the Ragna-mails are described as a mechanized angel. From that perspective, the angels draw their power from the God(dess), as the Convergence Space-time Cannons can only be activated when the song is sung.

Here they refer to it as "the god".

If I had to guess, I'd say that information came from the CD.



On another note, Crunchyroll or whoever really needs to hire better translators. If it was "the wind flies" then it would "kazega yuku" not "kazeni yuku".