Toby was presumably, a former criminal that allowed Dr. Stylish to experiment on his body in exchange for a lighter sentence.
Toby was one of Dr. Stylish's strongest henchmen. He had his body modified, becoming mostly mechanical. This made him immune to Murasame's poison. He had a lot of weapons implanted into his body, and couldn't feel pain. He was killed by Akame and Lubbock while attacking Night Raid's hideout.
Equipment and Skills
He had offensive attacks, and had a lot of weapons installed inside his body, including swords and guns in his hand, and even his mouth was equipped with weapons. However, because he couldn't feel any pain, he had many gaps for counter attacks, as stated by Akame during their battle.