Petra is a gloomy goth girl who begins to date Marcus Lopez during the Kids of the Black Hole arc. Her parents were both hippies who joined a death cult and met Master Lin at an orgy. They figured a way to relieve themselves of their parent duties with Petra was to dump her off at Lin's school, King's Dominion Atelier of the Deadly Arts. On Petra's 11th Birthday she found a mason jar with her mother's eye balls in the fridge. Her father explained that he had watched her mother die and that witnesses such a thing gives you strength and strips away your fear. Shortly after this, Petra went away to school.
Petra first met Marcus on top of a roof at King's Dominion. She was hanging out with Willie, Billy, Dan and Lex. Some time later, when Marcus was rejected by his friends, she invited him to hang out with her. Eventually, the two hooked up as Marcus continued his downward spiral of shame and worried about his friend turning against him.
When Master Lin soon announced the semester's final was to kill all the rats, those that have disobeyed the school's rules, both Marcus and Petra realized they had been labelled as rats. Marcus grabbed Petra and the two attempted to flee from their classmates. Petra concocted poison to help them kill several classmates that were pursuing them. They then grabbed Billy along the way, who agreed it was safer to be with his kind, the rats, then to be with others. Elsewhere, Viktor teamed up with Shabnam as they made plans to hunt down and kill Marcus.
They made a plan to kill Viktor. When Paulie bailed on them, Billy was chased and was left to improvise. Marcus and Petra caught up with Billy as the trap and found Billy had been beaten savagely. Viktor was sprawled out on the ground as the gigantic stone they rigged had fallen and smashed Viktor in the back. However, they were soon attacked by an explosive arrow. They escaped to the last place anyone would look for the three of them, F-face's old place, the Tenderloin. Marcus finally agreed with Billy and Petra to run from the school and stop playing this deadly game.
After hiding out in the Tenderloin for a few days, The trio are then tracked down by Viktor and his associates, forcing Marcus to act as a distraction for Viktor while warning Petra of his suspicions about Billy. After hiding in a room, Billy and Petra open up to each other about their pasts. However, Petra reveals herself to be the traitor within the trio after locking Billy inside the room with a bottle of poisonous gas, killing him. After dragging Billy's body from the room, she tells herself that her father was right that she would become stronger upon seeing someone die before her eyes.
The character was originally introduced in issue 2 of Deadly Class. She had a limited role and was referred to as Yolga. The character was reintroduced in issue 7 as Petra.While the series has never mentioned the name confusion, Wes Craig has confirmed they are the same person.