[Zetsuen_no_Myuu]

Uhuhuh, I saw that vid before already ^^ It's still not translated though. *cough*

The setting book for Seinarukana is 聖なるかな オフィシャル設定資料集, I believe. For the one that comes with EnA's SE, I think it's 永遠のアセリア スペシャルエディション同梱 設定資料集.

I think Narukana should be on the same level as Myuugi and Rogus (Eternal Sky drama CD spelled it this way) too. Unless of course, it's like you can't go against fate and destiny type of thing and the only thing that can trump them is a greater fate and destiny that comes from the unranked eien shinkens. Aside from Aselia and Euphoria, there should be another existence out there holding onto the final unranked, which would be Setsuna, the rival of Eigou (Eternity). Hijiri Takeshi, the 4th known rank 1 a subordinate of Setsuna and it's possible he/she is holding that last unranked.