The Persian is the tritagonist a mysterious figure from Erik's past. He knows more of the history of the Opera Ghost than any other character. The Persian leads Raoul de Chagny into the Phantom's lair in the original novel to save Christine Daae, and warns him to "keep his hand at the level of his eyes". He also saved Erik's life at some point, and would seem to almost consider himself Erik's friend were it not for the constantly opposed moral views they have.
The Persian was once the Daroga - police chief - in the Mazenderan Palace in Persia. Word of Erik's escapades had reached Persia, and the Persian found Erik and brought him back. They became acquaintances and Erik did him a few favors. While in Persia, Erik impressed the shah, but he learned too much about their secrets. The Persian was ordered to kill him, but he couldn't. He faked Erik's death, but was exiled and striped of his powers. He left Persia and went to live in Paris.
When Erik came to live in Paris, the Persian kept a close eye on him, not wanting him to get into any trouble. The opera house's workers and patrons paid him no mind, as he mostly watched from afar. When Christine Daae disappeared during a performance, he teamed up with Raoul de Chagny to go down to the Phantom's lair and save her. However, they get trapped in a torture chamber and nearly drowned. The next thing he knew, the Persian was resting in his home. He remembered seeing Erik, Christine, and Raoul together, but didn't recall the details.
He attempted to go to the police, but they didn't listen to him. Afterwards, Erik approached him and told him what had happened - Christine had kissed him and he had let her and Raoul go. He put matters to rest and never spoke of it, again. When an investigator had asked him about the Opera Ghost, he told him everything that he knew, and he constructed it into a story - The Phantom of the Opera.
Despite his sizable role in the novel, the Persian is almost never included in adaptations. His role is usually given to another character, such as Madame Giry in the 1986 stage musical, or averted entirely by making Raoul a more competent hero. There are only a few where he made the cut.
In the 1925 film, the Persian is portrayed by Arthur Edmund Carewe. In early cuts of the film, he was the Persian from the novel and had an identical role as he did in the novel. Later cuts of the film changed the character, revealing that he was a French inspector named Ledoux, who was only pretending to be Persian. This was a trend in early Hollywood, where a character of color was revealed to be white, such as Rudolph Valentino's character in The Sheik.
In the 1976 stage musical, the Persian takes on the same role that he does in the novel. His solo number in Act II, "Born with a Monstrous Countenance", was about the Phantom and his history with him.
In the 1988 animated adaptation by Emerald City Productions, the Persian fulfills much of the same role that he does in the novel. He guided Raoul down to the Phantom's lair and helped him and Christine escape in the end.
In Phantom by Susan Kay, the Persian plays an even larger role, starting off as the Royal Daroga of Persia. He is also given a name, Nadir Khan. Erik and himself were friends in the Persian court. Erik entertained his son and helped him in the last few months of his life. When Erik is to be arrested and sentenced to execution for knowing too much, the Persian risks not only his position but his life and allows him to escape. He only survives because his servant placed a dead body on the shores of the sea and dressed it in Erik's clothes and mask. The body was unrecognizable, so the Persian was not killed. Instead, he was exiled. But, due to his distant royal lineage, he was allowed a pension and came to live in Paris. When he once again meets Erik, he begins taking notes on him. It is a symbol of how well Erik thought of the Persian that he actually tried to keep a promise he made to him. As Nadir was releasing him years ago, he made Erik promise to commit no more pointless murders. Not only did Erik agree to the promise, but he tried, over the years, to keep it, and all but succeeded.
In the 1991 stage musical filmed and aired on PBS, the Persian was portrayed by Harsh Nayyar. Similar to the novel, he kept tabs on the Phantom, talking to Joseph Buquet about his encounters and to Raoul about Christine's sudden disappearance. After the Phantom kidnapped Christine, he was there to help lead him down to his lair. He stayed behind, after Raoul and Christine fled. When the Phantom threatened to kill him, he called his bluff. Before he exited, the Phantom said that he could follow him into the darkness forever.
In the visual novel developed by MazM, the Persian takes on the same role as the novel. He is first seen in the background as an NPC, unable to be spoken to. As the story progresses, he takes on a more active role.