Ser-Veresta (黒炉の魔剣), also known as Sword of the Black Furnace is an Orga Lux owned by Seidoukan Academy. It is currently being used by Amagiri Ayato, the second official user, with a compatibility rate of 97%. It had been previously used by Amagiri Haruka. It is also one of the Four Colored Magic Swords.
The Ser-Veresta has a large blade of flaming white light and black patterns that intertwine. Until volume 5, the Ser-Versta is too large for Ayato's preferred fighting style. However, an adjustment of Prana input, made by Julis and Ayato together, reduces the blade.
Claudia mentions that Ser-Veresta forms a blade made up of heat, which she mentions as being able to "disintegrates all that it touches, when it pierces, the world shall turn to purgatory" when asked about it by Ayato. It carries with it an intimidating history, feared by all the other schools.
The cost of Ser-Veresta is its high prana consumption rate, which would quickly dry up a user with normal prana. In addition to this, it has an incredibly demanding personality, resulting in incredibly low chances of getting a high compatibility rate. Even though, it acknowledges Ayato's prowess, it refuses to activate unless Ayato is giving his all in his unsealed state.
In addition to this, Ser-Veresta doesn't allow anyone else aside from its wielder to touch it. Julius, who has a high fire resistance, was burned after touching it.
It is capable of changing into a more suitable shape depending on its wielder, extending its blade after Ayato used Meteor Arts, which was explained as Ayato through Julius' assistance turned into a form longer than a katana.
- The blade of the Ser-Veresta is white in the light novel but is changed purple in the anime (though it started out white in the first episode it appeared in, only to turn purple moments later). Although, in the later volumes it did turn black true to its namesake as a black blade.