During the war he went on missions with the Diablerie. He once allied with the Dead Men to hunt Abyssinia.
Return of the Diablerie
Gallow rejoins The Diablerie with two other members - Gruesome Krav and Murder Rose. He was presumed by many to be the Diablerie's leader, until it was revealed to be Batu. He tries to recruit China back into the Diablerie, but she refuses, upon which Gallow attempts to kill her. He, Gruesome Krav and Murder Rose also attacked Tanith Low after Emmett Peregrine's death. Gallow later kidnaps Guild and is seen at Liffey Bridge during the exchange of victims.
At Aranmore Farm, he realises that the tattoo on his arm is not a shield against the Faceless Ones, as Batu had told him, but is, in fact, a beacon. He is forced to cut his arm off using a Cleaver's scythe so that he isn't possessed by a Faceless One.
Rise of the Death Bringer
Gallow appears again in Death Bringer. He has a new arm, which he says was taken from an "unwilling donor" and which he covers with a glove. Having lost his faith in the Faceless Ones, he approaches China Sorrows so that they can bring down the Church of the Faceless. After some scrutinising, China accepts his request. Gallow mentions a list of twelve names who are sponsoring the new Church of the Faceless. China asks him to retrieve the list so they can assassinate the sponsors, along with Eliza Scorn.
China guesses Eliza is planning to meet with the twelve at the Requiem Ball. Gallow manages to retrieve the list and he arranges to meet with China outside Gordon's house, where the ball is being held. But when China gets to him, she finds Gallow dead in his car – with the top of his head on his lap. He was presumably killed by Eliza. On the dashboard a note is left, reading: "Too late, sweetie".
Magic and Abilties
Gallow was an Adept, but his exact ability is unknown. He was proficient in hand-to-hand combat, however, as he easily dispatched Remus Crux with his bare hands. He also used a gun as a weapon.