Little is known of Arnold's early years, but he eventually became a trader, dealing mainly in black market goods. He has never been affiliated with any particular gang, though he has sometimes worked with any number of them, including LandOrder, InterGang, and independent gangs of various villages. Mostly, though, he works alone.
He is also known to have long maintained strong ties within the 'Rat communities of various villages. For this reason, some people refer to him as "Arnold Streetrat," though this is not a name he likes. In fact, the only person he doesn't seem to mind calling him "Streetrat" is Tiejo Streetrat, whom he met in 912. He met Tiejo through Dave Road, a street rat he had met in Triscot sometime between 908 and 912, and who had been a childhood friend of Darius Lonewander. A few weeks before Arnold met Tiejo, Darius had met Tiejo, and started a group which originally intended to rebel against the Second Order. While Tiejo had been contacting various 'Rat friends of his as he traveled between villages with The Chaos, and asking them to be ready to help his new allies, should the need arise, Arnold already had many contacts. So, Tiejo formed an alliance with him when they met, and between the two of them, there would soon be very few 'Rats in the villages of Near Land, First Land, and Jump Isle who weren't prepared for action when the time came. That time finally came a few months after Arnold first met Tiejo, and the 'Rats of Triscot helped hold off the regiment from Near Port, who were in pursuit of the regiment from Kimrin, which defected to become the foundation of the fledgling Chaos Army. Later, the 'Rats of various villages would assist the Chaos army in the Chaos War.
After the war, Arnold helped Tiejo and his other allies among the 'Rats form the Allrat Fellowship, though it isn't believed that Arnold remained an active part the fellowship, after it was organized. He returned instead to his old career, though he has of course continued to maintain friendships with Tiejo and any number of other 'Rats.
The derivation of Arnold's chosen surname is unknown.