Device

Device (デバイス, Debaisu ) are weapons that a Blazer are able to manifest from their souls. At times Devices are referred to as Holy Swords, Demon Bows, Cursed Tools and Blessed Tools.

Summary
Devices are the materialization of a Blazer's soul as a weapon, which can be used in battle. A Device takes on an assortment of different forms and abilities based on the Blazers themselves as shown with Kuraudo's Orochimaru which can extend and move at will. These Devices can take form as simple normal weapons ranging from swords to more modern weapons such as firearms. A Device is able to take form as things that are non-offensive related to the Blazer's magic like the Brush of Demiurge manifested by Sara Bloodlily whose form is that of a paintbrush and palette pertaining to her power to manipulate the concept of "Art".

A Device also serves as a medium for Blazers to utilize their Noble Arts, which is their Trump Card in battles.

As the manifestation of their souls, Devices are able to withstand great damage without being broken, however, it doesn't mean they're indestructible if their Device does break it lead the Blazer to lose consciousness. There are a lot of Blazers such as Nagi Arisuin who are able to summon multiple of the same Device, although this is due to it being apart of their nature.

Illusionary Form
A Blazer can summon their Devices into their «Illusionary Form» for practice, mock battle, or if the Blazer doesn't intend to cause real damage, causing damage to their stamina instead of physical damage. Although a Device in its Illusionary Form cannot cause damage or kill, if enough overwhelming power is used, then it can put people in a comatose state.

Device Reconstruction
"—The Device had changed this much. It was beyond common sense, because a Device reflected a Blazer's inner spirit, his personal values, and aesthetics, personality, and lifestyle—how could it be changed to this degree? It couldn't be. Imagine the determination and the kind of training Kuraudo had undertaken to abandon all he had been, to kill off all he had been so completely was…!"

- Ikki's thoughts on the Device's Reconstruction

There are rare occurrences where a Device can change and/or even evolve due to reflecting the inner spirit of the Blazers who had manifested them. Therefore, if a Blazer were to "rebuild" themselves thus causing a drastic shift in their original beliefs and ideals, which results in their Device taking one a new form based on their change. This is first shown by Kuraudo Kurashiki after losing against Ikki causing him to desire to become stronger like him, as such he learned the Ayatsuji Ittou-ryuu adopting to a disciplined form, which resulted in his Orochimaru becoming two instead of one; both blades has an edge on both ends like a western blade instead of a saw-tooth like before.

The second occurrence being Stella Vermillion who during her fight against Fu Xiaoli, a desperado, didn't desire to give up on her ego (self) causing her soul to undergo a drastic evolution due to her extreme willpower causing Lævateinn to become a golden double-edged broadsword longer than herself and thicker than a man's arm.

Trivia

 * In the anime, summoning Device's are sometimes made more dramatic. For example, Ikki would "draw" his device as he would for a normal sword from its' scabbard.