Device

Device are weapons that a Blazer are able to manifest from their soul. At times Devices were referred to as Holy Swords, Demon Bows, Cursed Tools and Blessed Tools.

Summary
Devices are the materialization of a Blazer's soul, in essence, it is a crystallization of magic power, which can be used in battle. As such, these weapons can withstand an incredible amount of damage without being broken, but it doesn't meant they're indestructible. If broken, however, the Blazer loses consciousness, at least under normal circumstances, as those with strong enough wills can remain active for a time. There are those such as Nagi and Tendou, who can manifest multiple copies of their Devices.

These takes on numerous forms based on the Blazer, as first shown when Kuraudo's Orochimaru can extent and move around on command. Others can take form as items meant to be medium for their abilities and Noble Arts: non-offensive, such as Sara's Brush of Demiurge (Art) and modern, such as Kurono's Propator and Ennoia (Time).

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.