A Shueisha team.
Dark Signers's HistoryThe Dark Signers were a group of Duelists resurrected and in the service of the Earthbound Immortals, who served as the evil counterparts to the Signers and were the primary antagonists for the second arc of Yu-Gi-Oh! 5D's.
When a person died, he or she was given a chance to live by becoming a Dark Signer at the time of their death. If they displayed a great will to live or a reason for revenge, an Earthbound Immortal may spare them (provided they agree willingly, whether or not they remember doing so after being brought back), turning them into the Dark Signers in the process. As the Dark Signers, those individuals were given a great power and a great lust for revenge. All of the Dark Signers, with the exception of Roman and Rex, held some form of grudge against (or connection to, in the case of Devack and Carly) a Signer, which would provide another answer to why the Earthbound Immortals chose them. Due to this phenomenon which derived from the Netherworld itself, there was no way to revert the transformation or revert to their former selves, and were said to be no longer of the living world. If they turned over a new leaf in a Duel, the Earthbound Immortal would take over them and continue the match (however Akiza noted, their control can potentially be broken if the Earthbound Immortal is destroyed without getting rid of the person's Life Points).
Thus because of this distinctive group of individuals already had died once, it is seen that once they have been defeated in their own Shadow Duel or Shadow Turbo Duel for that matter, their departure from this world would be completely different. As instead of simply dying like a normal human being, they instead would wither until they became dust when they were sent into the Netherworld.
They were capable of using a distinctive type of monsters known as Dark Synchro Monsters which were black lined. Their signature card are the "Earthbound Immortals", along with the use of Field Spell cards in order to maintain the effects of these powerful beasts in a Duel. There were only five Dark Signers at any given time, each one possessed by a different geoglyph. In the anime present altered time-line, a total of seven awakened, due to the fall of others. Devack was 'succeeded' by Greiger and Rex was revived after his Duel with Roman.
Dark Signers are shown to have a red Criminal mark-esque patterns on their face and black sclerae. The only exception is Kalin, whose original Criminal mark became his dark mark; even after his revival, the Criminal mark did not vanish.