Origin  

Tommy was born the son of Hadley "Rip" Jagger, the first Judomaster. He grew up to be an exceptionally skilled martial artist.  

Creation  

Tommy Jagger was created by Greg Rucka and Jesus Saiz in the first issue of the Checkmate ongoing series. He was one of a handful of new characters that would populate the cast of the book. 
 
Later in the series, it was established by Rucka that Tommy was gay.

Major Story Arcs

Game of Kings    

When Checkmate was reorganized under the United Nations, Tommy Jagger was recruited to serve as the White King's Knight. He first served under Alan Scott and then continued his service under Mr. Terrific's time as White King after Alan was forced out of Checkmate for taking too active a role in a covert operation that went bad in China. A small Checkmate team, including Tommy, had been discovered by the Great Ten, and it took Alan's direct involvement to resolve the situation without the loss of life on either side.
 

Tommy inevitably encountered his father's killer when he and Fire are sent on a mission to Bane's home country of Santa Prisca. There to discover the one tampering with the country's elections, Tommy catches Fire burning the remains of Computron as part of a side arrangement with Amanda Waller.  The flames caught the attention of Bane, who appeared and was anxious to fight Fire. However, in order to allow Fire to escape, Tommy battled Bane. In the end he defeated Bane, but chose not to kill him. 

  After the mission, Tommy exposed Fire for actively sabotaging their mission. He didn't have proof beyond his own words, but she immediately confessed that his accusations were true.

Checkout

Checkmate decided to use the Outsiders for a joint operation on Oolong Island, but getting the Outsiders to the table was an issue. Tommy was assigned to bring in Katana. In doing so, he ambushed her on a bridge by posing as a harmless jogger. He abducted her quickly and easily.

He later took part in the mission to Oolong Island, teaming up with the Outsiders. There seemed to be no hard feelings between him and Katana. He was assigned along with Grace, Thunder and Fire to cover the infiltration team's retreat. While staking out a position to do so, he and Fire had words. He informed her that while others may have forgiven her for what went down on Santa Prisca he had not, so even if he were not gay, she would still not be his type.

Final Crisis

For further details: Final Crisis 
On the day evil won, Tommy went with a significant portion of Checkmate to Antartica to ensure that the Code Zoo and Arcane Locker were not compromised. He expressed annoyance with the assignment, preferring to have remained at the Castle where his former White King, Alan Scott, then was. While outside the facility with Fire, he was ambushed by Ice. She had already been taken by the Anti-Life Equation and spread it to him and Fire. They then breaches security, allowing Ice and the Anti-Life Equation to quickly compromise nearly everything. Mr. Terrific and Khalid were able to secure the bunker with the Code Zoo and Arcane Locker.

Attempts to break the bunker's security were futile, but Tommy and the others were at least able to keep Mr. Terrific trapped inside with his few allies. That was until Mr. Terrific activated the remaining OMACs in the world and had them come to his position. Tommy was taken down by the siege of OMACs.

Powers and Abilities

Tommy Jagger has no metahuman powers. But he is a highly skilled martial artist, having expertly defeated the likes of Bane and Katana. However, it is not known how his skill compares to that of DC's upper tier of martial artists such as Bronze Tiger, Connor Hawke or Lady Shiva. 
 
He is also a well trained agent of Checkmate, being skilled in weapons usage, military tactics and espionage.