William Lloyd was an agent for the British Rite of the Templar Order who served as the right-hand man to Harry Parkes, the British Consul to the Tokugawa shogunate during the Bakumatsu era of the late Edo period in Japan.
In 1855, Lloyd was sent to Edo by the British Templars with the mission of restoring the power of the Japanese counterparts, who had fallen into obscurity since the end of the Sengoku period and the Assassin-backed reunification of Japan by their most important ally, Tokugawa Ieyasu. As a testimony to his skills as a swordsman, Lloyd was one of the few foreigners who were granted the right to carry a custom made Japanese saber, with the locals believing that his talent was the result of a pact he made with an oni.
At some point before 1867, thanks to the influence of the Order, Lloyd was appointed as the assistant of Harry Parkes, the British Consul to Japan. As the main counselor of the Consul, Lloyd then used his influence to weaken the Tokugawa shogunate. Lloyd's mission was successful as the political landscape was so deteriorated that Emperor Meiji and his allies would instigate an uprising against current shōgun Tokugawa Yoshinobu and clans loyal to the shogunate. One night, he was nearly killed by the shinobi Issa, who infiltrated the British consulate in Edo to assassinate Harry Parkes. While poisoned, Lloyd thwarted the assassination attempt and severed one of the Assassin's hands before Parkes finished him off with a firearm.
As part of his mission to restore the Imperial power, Lloyd also wanted to obtain the Musashi Masamune, a powerful sword that once belonged to the legendary Japanese rōnin Miyamoto Musashi, to bolster the prestige of Emperor Meiji. Lloyd and his strike team of elite mercenaries assaulted the Tokugawa camp, planing to seize the Masamune from Saigo Kayano, the obese lord who owned it. After they killed a begging Kayano and his retenue in his tent, Lloyd was leaving with his prize when he stumbled again upon Shiba Ibuka. Disgusted by the cowardice that he previously showed under Kayano's tent, Lloyd tried to execute the terrified samurai. But, to the Templar's surprise, the young man parried all his attacks, acting on instinct only. As he prepared to leave, Atsuko, the disguised sister of Ibuka, jumped on his back but he threw her back to the ground and fled on a horse. However, as he reached for the blade once safely outside the camp, the furious Templar discovered that Atsuko took it back without him noticing. Back in Edo, Lloyd reported his failure and was given a new mission by his masters, to win the war at all costs. 
During the Battle of Aizu, Lloyd recovered the Miyamoto Musashi from Matsudaira Katamori, as the powerful daimyo took the relic for himself after the death of Saigo Kayano. Confronted by Atsuko, he quickly dispatched the girl, leaving her uncounscious and bleeding to death. However, he met his end when he was slain by Shiba Ibuka after they met again. Indeed, the petrified Ibuka overcame his mental block after Lloyd inflicted him a gaping and fatal wound, freeing the young prodigy from his fear of death. Despite his death and failure to secure the blade, the Templar mission was a success, as the young Mutsuhito emerged victorious from the Boshin War, taking a new name and establishing the Empire of Japan.