Toby Mercurio was a marine raised on Korhal. Fellow Styrling Academy student Arcturus Mengsk considered him to be a person of "low breeding", as his family had only recently come into money and he continued to use Gutter slang.
Toby Mercurio was able to scrape by academically, but it was only his above average performance in padball that allowed him to graduate. Without any real qualifications, Mercurio was only able to find employment at one of his father's plants in a series of paper-shuffling jobs, failing spectacularly in all of them. One afternoon, he got particularly drunk and woke up with a massive hangover and signed enlistment papers for the Confederate Marine Corps.
He ironically ended up serving in Dominion section under Mengsk. Despite Mengsk's efforts, he couldn't bring Mercurio up to the same standard as the rest of his unit and could tell that Mercurio wasn't meant for the profession. The odd one out in the unit, Mercurio usually looked depressed and rarely joined in the squad's banter.
Mercurio's first taste of combat came in August, 2480, a period when he and the rest of the section were supposed to be on leave. Along with the 33rd Ground Assault Division, Mercurio and the unit successfully overcame the resistance of Kel-Morian miners on Sonyan refusing to be evicted from their claim. Alongside fellow section members Chuck Horner and Yancy Gray, Mercurio successfully performed a flanking maneuver in the battle and even emerged in what passed for a good mood for him.
Whatever good Sonyan did for Mercurio's personality didn't last however. He remained silent as a norm over the next five years, serving the Confederacy on worlds such as Parragos and Pho-Rekh. However, in 2485, his miserable streak came to an end. Dispatched to Noranda Glacier on Onuru Sigma to evict Kel-Morian workers, Mercurio was killed by a goliath in the resulting battle.