While participating in a physicality test, Dev-Em killed team member Kell-Ur, in an attempt to better his odds of passing the test. He then assaulted Kara Zor-El, after she learned of his actions. For his crimes, he was put in front of the Kryptonian Law Council, who sentenced him to death. Upon objection by the other ranking members of the council, the decision was made for Dev-Em to instead remain in custody.
He later escaped, and sneaked onto Scout Ship 0344. While the crew members were in cryosleep, Dev-Em awakened and killed all of them except for Kara Zor-El, and changed the ship's course to head for Earth. After Kara awakened, the two of them fought, while the ship crash landed into Earth's atmosphere. Kara attempted to control the ship, but it crashed in Ellesmere Island, Canada, leaving the fates of both of them unknown.
Kryptonian physicality test
"We're simulating the harsh and unpredictable conditions Explorer's Guild members potentially encounter, Kell. There's no telling what we could find before the terraforming begins. Or what might find us."
Dev-Em was born on the distant planet Krypton around 16,000 B.C. At a young age, he joined Krypton's terraforming project. While on the deadly physical test that would determine the best candidates to go on to space colonization missions, Dev-Em attempted to get an advantage over the other candidates. He killed his main competition, Kell-Ur, who was the lover of Kara Zor-El. Upon witnessing his death, Kara beat Dev-Em in combat and subdued him.
Trial at the Kryptonian Law Council
"Accused Dev-Em, after five weeks of deliberation, we find you guilty of assaulting Kara Zor-El and murdering Kell-Ur. Krypton's first murder in a thousand years. Your blatant disregard for the life of your fellow students is troublesome. As a result of your actions, I hereby recommend to my fellow council members death--"
"No, Dar-Enx! We are not barbaric, like the Thanagarians! Our laws are not "an eye for an eye, a life for a life"!"
Five weeks after the murder of Kell-Ur, Kev-Em was put on trial in front of the Kryptonian Law Council for Krypton's first murder in centuries. Dar-Enx recommends that Dev-Em be given the death sentence, but the rest of the council decides against it, not wanting to be "barbaric" like the Thanagarians. Instead, Kev-Em is sent to prison, and remains in the council's custody.
Fight on Scout Ship 0344
"You've been asleep for a long time but I'm glad you're awake now. Hello, Kara."
Sometime later, Dev-Em is spared and escapes prison. He stows away on Scout Ship 0344, which has Kara Zor-El aboard. While all the crew are in cryosleep, Dev-Em awakes them before killing them afterwards and changing course for Earth. Kara awakens and discovers the bodies of the crew members and battles Dev-Em as the ship approaches Earth. Kara attempts to turn the course of the ship, but it crash lands into Ellesmere Island, Canada, leaving the fate of Kara and Dev-Em unknown.
"And why should I follow your orders, Kara Zor-El?"
Kev-Em was ego-maniacal, obsessed with controlling Krypton's future for his own benefit. He had a distaste for authority, ignoring the orders of Kara Zor-El.
To be added
"That seems like a slight over-simplification."
It is suggested that this article, or a section of this article, could benefit by being expanded upon.
In DC Comics, Dev-Em was a juvenile delinquent on the planet Krypton who became imprisoned in the Phantom Zone. Eventually, he escaped during the 30th Century, where he turned over and became a teenage superhero.