Larry Stohler was originally just a high-society gossip. He often saw Hunter Rose, and they often joked together, poking fun at each other and the rest of posh society. However, he once attended a party in which Rose, in his guise as Grendel, poisoned Barry Palumbo and briefly took Barry's niece, Stacy. Rose was missing from the party for some time. He worried that his absence would be noticed, and that people would figure out that he was Grendel.
However, while Larry Stohler did in fact figure out exactly that, he decided to help him instead of expose him. He misdirected the others at the party so Rose's absence wasn't missed. Later, he told Grendel what he had done. Grendel would normally have killed someone who put him in such a vulnerable position, but he liked Larry's cheek, and instead made him his assistant.
From then on, Stohler was an invaluable help to Grendel. He provided him with society information, and also helped to coordinate his criminal empire. For instance, once he elicited secret information from a Bolivian man who was smuggling drugs into town without giving Grendel his cut by pretending to be a debauched rich man looking to score some of his cocaine. He was also Rose's right-hand man when it came to Stacy; he was, absurdly, the only guest at her birthday party, and looked after her when Hunter went out as Grendel right afterwards.
While Grendel was still beginning to control the city's crime families, Rose had a crisis of self-confidence; unbeknownst to him, he was being tracked by a Dire-Imp, and he had an eerie feeling of being watched that led to a feeling of worry in everything he did. Stohler noticed, and while he continued to provide good advice to Rose about how to help consolidate his power, he began to worry about his boss. He helped Rose make their plans against an especially troublesome Korean syndicate. After that problem was solved, Hunter met the demon, which showed him the future, including how the spirit of Grendel would take over the world. Hunter wrote about it all in his journals. Angered by the whole affair, he then tossed the journal pages in the fire. Stohler then secretly grabbed the papers out of the fire and kept them.
Sometimes he took a more direct hand in criminal matters. Once he poisoned a stoolie after he passed false information to the police for them.
He was especially involved in the Seaboard Massacre, in which Grendel had all his rival crimelords assassinated. Stohler traveled around the country spying on them, and provided Rose with important information on their activities. He also helped Rose tape his taunting call about the massacre to the police--a call that was overheard by Stacy Palumbo, and which ultimately led to Rose's downfall.
When Stacy later tricked Argent into thinking that she had been kidnapped by Grendel and sent a message to Rose saying that he wanted to meet, it was Larry that gave Grendel the message.
When Grendel was killed, Larry read and burned his missing journal pages about the demon and its prophecy of Grendel's future world domination. Because the pages were burned, the world would have no warning of its dire future. The police soon showed up at his door, and Stohler killed himself with a pistol.
In the Batman/Grendel crossover Devil's Riddle/Devil's Masque, Larry is once again seen as Grendel's able right-hand man. He provides Hunter with travel arrangements, finds information on Batman and his rogue's gallery, easily elicits classified information from Lloyd's of London, and arranges the kidnapping of a young child.