Black Battler

Battler Ushiromiya at one point, desperate, countered Erika 's theory with a counter-theory of himself being the culprit, and when Bernkastel created her game, Black Battler was a game piece create by her desire.

Black Truth of Death
He appears to be just Battler in a dark suit, but that's all the power of his extremely convincing deceptive personality, as his true self is that of a sadistic killer, who acts stone-cold at all times save for his outbursts of maniatic laughter.

In Bernkastel's game he was the Culprit, who had lied about his parent's death, and they carried out the murders until they killed everyone. However, he only did this only because of his culprit designation, and expressed that he regretted having to be the Culprit.

This means that Black Battler was never truly "real".

Season 3
When Chris-chan tried to use The Focusing Stone's power to bring the Dimensional Merge, all he did was merely merge himself with his magination of Sonichu, as Chris always wanted to be Sonichu(Who was a Mary Sue abstraction of himself), becoming the Abomination. When Battler used The Focusing Stone to fix the Dimensional Merge, it somehow brought Black Battler into this world.

For the first time, Black Battler is "real" outside the game, and as a way to take revenge, he sent Battler along with 17 of his friends and trapped them in the Meta-World inside a game of their own.

Episode 5
Upon returning, he locked up on Battler's office, probably scheming his plans, when Kinzo Ushiromiya came to confront him, however, Battler didn't open the door until when he had lost hope and was leaving, but when Kinzo went in in, he shot him dead. Black battler have all the powers that the regular battler have but is slightly weaker.

Episode 6

Later on, when Agent 47, and later Max Payne came to his room, he locked them inside, and upon opening it there was no trace of anyone there, the current whereabouts of 47 and Payne currently unknown.

Episode 8

Agent 47 announced his cooperation with Blackler, and that he killed Kinzo and assaulted people backstage.

Episode 9Saihara reveals' 47's plan: To make everyone believe Black killed Kinzo and that he was real, when he was merely an distortion in reality, and so he would replace Battler and erase him. However, when Battler returns, he is the one that can defeat Blackler as the two are competing for the same spot on reality.

As the both fight each other, they throw Red Truths in trying to prove which one is real, and Battler manages to overcome Blackler. After the match, Battler restates the whole case in Red, and uses the to deny Blackler from reality.

And so, Black Battler was banished from this reality, but will he return someday...?

Season 6
With wild rumors of sightings of previous enemies of TFR returning, Kojima welcomes a group of men into his office who were running late: Kojima's Ruinous Powers.

Episode 16
Blackler and Sonichu fight Kasuga Ichiban and Agent 49, and despite Chris-chan being defeated, Blackler defeats both of them easily, but Suou's group gets the upper hand against Kojima, and Blackler escapes.

Episode 17

Blackler reunites with BANS, who accepts his culprit self fully, and both fuse to become Shadow BANS. After defeating his opponent, however, Agent 49 manages to dispel his power and send him back to Hell.

Trivia

 * Despite the similarities in name, he is not related to Black Ref.
 * Black Battler is actually Battler's shadow-self, and in Season 3, it was actually Nyarlathotep instead of the true incarnation of his shadow.
 * Coincidentally, Suou Tatsuya was the first one who noticed Black Battler's appearance in the arena, further establishing the relation.