A Drive-Union, abbreviated sometimes as a D-Union or Union, is a human being with a crystal imbedded within them. Through the use of their crystal, a Drive-Union is able to access their Drive at the cost of the pollution of their soul.
There are seven phases that the crystal of a Drive-Union can go through, which affects their abilities both physically and mentally.
Drive-Unions are a rare naturally occurring phenomenon. A crystal forms within the body and eventually attaches itself to the nervous system of the afflicted, thereby corrupting it, which then begins to effect their behaviour. Once the crystal attaches itself to the nervous system, its removal will kill the Union. After the Wadatsumi Incident, Drive-Unions began to become more common around the area of Shin Yokozaki City. In response to this, the Mitsurugi Agency had their main public objective stated as the capture and treatment of all Unions.
Unions who existed before the Wadatsumi Incident are known as Irregular Types. Little information about them or their numbers is known. Another unusual type of Union is the Strange Reds, a trio of Unions who have regressed into Phase 0 by continually consuming the crystals of other Unions. They are named for their unusual red crystals. The serial killer Ripper is the only known Irregular Type, as well as the only known Strange Red.
Once a crystal embeds itself within the Union, they are immediately capable of using their Drive on instinct by absorbing seithr around them. At this same time, regardless of its integration into the nervous system, a personality shift is triggered. The more the Drive is used, the more the soul of the afflicted is corrupted until, finally, the Union dies from overuse. Death in this condition causes the Union to dissolve into seithr. The only known Union to survive the condition and become human again was Akira Kamewari, who ripped his crystal out before it integrated itself into his nervous system.
One of the Ten Sages, Sechs, became a Union at an unknown time, acquiring the Drive Deadly Sign, which allowed him to turn others into Unions. He used this ability to great effect, turning fellow Sage Acht into a Union, as well as Akira. He attempted to turn both his father Lord Stroheim and a random man into Unions, but neither were able to control their crystals. A crystal which cannot be controlled will consume too much seithr and result in a Gain Art, causing the host to quite literally self-destruct.
Yuki Himezuru is a doctor who specializes in the treatment of Drive-Unions. It is her belief that the conventional urban legends of vampires and werewolves stems from the existence of Unions. The only thing capable of cutting through a crystal is the Signati Gladio Crystalis: Murakumo.
- Phase 0 - crystal color is red
- Phase 1 - crystal color is transparent. All Unions start in this phase
- Phase 2 - crystal color is light blue
- Phase 3 - crystal color is blue. At this point, the Union will become mentally unstable
- Phase 4 - crystal color is dark blue. At this point, the Union will become delusional
- Phase 5 - crystal color is between dark blue and black. At this point, the Union will become insane
- Phase 6 - crystal color is black. At this point, the Union will begin dissolving into seithr.
A Drive-Union can slow their crystals progression by refusing to use their Drive, but progression is inevitable without treatment. Only Phases 1 - 4 can be treated.
- Ripper (Irregular Type) - Drive: Scissor Hands
- The original Touya Kagari (Irregular Type) - Drive: Unknown, but presumed to be Bloodedge
- Acht - Drive: Veil Skin
- Akio Osafune - Drive: Iron Shooter
- Akira Kamewari - Drive: Hekatonkheires
- Artillery - Drive: unknown
- Goro Joizumi - Drive: Screaming Jaw
- Sechs - Drive: Deadly Sign
In the Mei Route of XBlaze Code: Embryo, Mei Amanohokosaka is turned into a Union by Sechs and develops a Drive known as Blood Cain.