Eye of the Blue

The Eye of the Azure (蒼の眼) is the title given to the individual who holds the true power of the Azure and in turn, the Azure Grimoire.

It is unknown how one can actually become the "Eye" as the only known Eyes are Mu -No. 12- and Noel Vermillion, the original Boundary Interface Prime Field Device who eventually became the Master Unit, but it is implied that one cannot be human as the power of the Azure would corrupt their body and mind (similar to Arakune). Being the Eye grants the bearer numerous abilities, one of which is, of course, being able to use the power of the Azure but also allowing one to see another person's distant and previous memories by touching them, as seen with Carl Clover, Tsubaki Yayoi, Hazama and Lambda -No. 11-.

Due to comments dropped by Rachel Alucard, it is also possible that becoming the Eye would make that being an immortal similar to her.

According to Rachel, Noel was selected as the "Eye", Successor of the Azure, specifically for breaking the endless loop, even chosen in the exact moment she broke it, which was in accordance with the Master Unit's wishes.