Blackthorn (블랙덤, Beullaekdeom, lit. Black Bush) is a phenomenon that occurs as the last stage of Mind Corruption (정신폭주, Jeongsinpokju, lit. Mental Congestion) after a Contractor overuses their Dragon Artifact. The outcome results in the victim's body being covered in red-black spikes; it is called Blackthorn because of its resemblance to a burnt thorn bush.
Every time a Contractor uses an Artifact, they develop a small portion of Blackthorn in their blood. The rate of consummation from Blackthorn defers from every Contractor depending on their tolerance and strength in mentality. Once a Contractor exceeds their level of resilience, Blackthorn explodes out of their body and completely envelops them in it.
Stated by Lupenin Laiden, the shape of Blackthorn helps determine how the user was killed from the Artifact. Besides Contractors, people who are not capable of wielding Dragon Artifacts also turn into Blackthorn when trying to activate one.
People infected by parasitoids become Blackthorn after the parasite leave the host's body.