Salman Haseem was born in Ādīsi Geneti to unscrupulous circus owner Iago Haseem, and was callously used by his father as an attraction in his Haseem Travelling Circus after he was found to have a nervous disorder which made him unable to feel pain or indeed any physical stimulus. His act largely consisted of fire-eating, fire-breathing, passing sharp objects through his skin, sword-swallowing, walking on broken glass, lying on beds of nails and similar extremely dangerous stunts. As a result of this combined with his disorder, the only reason he remains alive is because of healers as he was a very profitable act. This has left him heavily scarred with much of his fur missing. The extreme abuse that resulted from his "gift" left him as a misanthropic sociopath with pyromaniacal tendencies. As such he is the least sociable of the escaped freaks and is purely kept around from a sense of solidarity rather than because anyone actually likes him.
Following his escape in And the Freak Shall Inherit... with the rest of the freaks, he somehow ends up on the border between the Empire and Manzil, causing something of an international incident due to burning down a number of Manzili military border posts. He has also gained pyromantic magic abilities from somewhere.
He reappears in Beneath the Mountain as a major supporting antagonist, having apparently joined the cult of Nox who has proceeded to further feed his more sadistic tendencies and enhance his pyromantic abilities to a genuinely frightening degree. He has also teamed up with two other cultists along the way, Al'Vn and Kilik Woteh (neither of whom particularly like him and indeed Kilik followed his orders out of fear of death rather than loyalty to the cause or to him as a person). He also appears to have been granted some kind of enhanced durability, as he survived numerous potentially fatal blows with little major injury (though did still need to relocate various bones.)