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

In Bernkastel's game

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 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 Time Merge, it somehow saw Battler's culprit theories in his head and assumed it was the closest to Battler's perception of itself, somehow bringing Black Battler back to life once again.

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 6
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 7
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 9
Agent 47 announced his cooperation with Black, and that he killed Kinzo and assaulted people backstage.

Episode 10
Saihara reveals' 47's plan: To make everyone believe Black killed Kinzo and that he was real, when he was merely a glitch in reality, and so he would replace Battler. However, when Battler returns, he is the one that can defeat Black as the two are competing for the same spot on reality and exist on the same plane.

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

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

Trivia

 * Despite the similarities in name, he is not related to Black Ref.