Blackmore has short blonde hair that is shaved on the sides. His skin is a pale white and his youthful face is a stark contrast to his body, taller than most his age and broad-shouldered. Blackmore's eyes are a green color.
When he first meets the Port City Eight and leading up to their departure to Aiola, Blackmore wears a dark purple suit alongside a black t-shirt and combat boots. As of "The Less I Know the Better," Blackmore wears a white polyester jacket with a golden image of a scorpion and black jeans, alongside a magenta undershirt.
Blackmore is blunt and matter-of-fact, normally finding himself speaking very frankly. On occasion he acts cocky, but he rarely sugar-coats anything he says.
Blackmore grew up in Thales, in a Nuyovian area of Polswich. He joined the Svatovid at the age of fourteen, meeting one of their spies who was only a year older than him and forming a friendship. His friend had ambitions to become an underboss, and so Blackmore became his bodyguard and his best tool for intimidation. When the Port City Eight launched a direct assault on Alchemilia Corporation, Blackmore was sent alongside an assassin to send a message by killing the people who ended Gabriel Alchemilia's reign over Silivia.