Knights of Tartaros

The Knights of Tartaros (タルタロスの騎士 Tarutarosu no kishi) are a guild and an order of 17 extremely powerful dark mages. They are currently led by Barbatos and have been active for 10+ years. This guild's mission statement is to "rock the boat" and "create an uncertain future", their targets are usually high-level heroes and guilds that stand for order and peace. They revel in the chaos that uncertainty makes and enjoy watching how the death of a hero can affect the outcome of the future.

Location
Due to the fact that the guild's activity involves assassination the actual guild hall is largely unknown outside of its members. It is rumored that the building is underneath the ground due to the likeness to the mythical Pit of Tartaros from Greek Mythology.

The guild building itself is described as an underground fortress and bunker. All areas of it, including the rooms and hallways, are lined with concealed magic traps that can be activated at any time. These traps vary from illusion spells that can make the trespasser see walls of concrete instead of corridors, to magic circles that fire condensed magic energy. These traps also include the formation of golems, familiars, and other various controlled beasts that scour the halls hunting the unfortunate souls.The layout of the building is also designed to confuse trespassers with various twists and turns and endless halls of identical-looking rooms. Only knights correctly know how to traverse the building without getting lost.

History
The founding of this guild is mostly shrouded in mystery due to the fact that current master was in hiding for most of his life. After obtaining his magic, Barbatos recalls an apparent dream in which a "god" told him to form the guild in the name of chaos. After building the guild building Barbatos went out to recruit some like-minded individuals.

Through his skills of tracking and stealth, Barbatos found the first couple of his knights. These "First Knights" are the most experienced and deadly members barring Barbatos, and while they are all loyal to the Knighthood, they each have their own desires they wish to fulfill.

Guild Spells
Key of Salvation (救いの鍵 Sukui no kagi): The Key of Salvation is a mark branded onto all the members that acts as the key to the building. This key does everything from authorizing the traps to simply unlocking the doors, the mark, in fact, is actually the guild mark that is stamped onto every member. The mark doesn't need to touch the desired object to activate, instead it only requires the knight's willingness to use it. This makes it so no self-righteous mages can sneak in without having the mark. This mark also gives access to the impressive armory of magic weapons collected over the years from buying, stealing, and looting them off the bodies of fallen heroes.