Blue

The Azure in BlazBlue, is located inside the Boundary and described as being the true power of the Boundary (or perhaps beyond the power of the Boundary). The Azure Grimoires are seemingly the only grimoires that have the power to tap into it. Yūki Terumi was the one who created the prototypes of the Azure Grimoires along with his improved Azure Grimoire he possesses. Ragna is able to access the True Azure through the use of his imitation Azure Grimoire along with the Idea Engine. Noel, unlike the other Prime Field Devices, didn't need the Azure Grimoire to become Kusanagi because she already inherited the Azure.

Arakune is obsessed with finding the energy of the Azure. He hunts down those that exude the same energy or traces of the Grimoire. Coming into contact with the energy is what caused his form to degrade into the monster that he is. During his story, he manages to warn Litchi that she is being devoured by the energy as well, and that she should resist the temptation to embrace it any further.