The Slams, also known as the Slam gang, were a gang of young thugs from Mamendin, in the Galactic Core, starting out there with con jobs and ID thefts. They then roamed the galaxy, mostly in the Core, pulling scams. They were the gang who notoriously heisted the entire treasury of Vuma; the crystalline vertex they stole nearly bankrupted the planet.
Roper Slam, a con man, and Valadon, an ID theft expert, were the gang's founder-leaders. The only other gang members included Waldo, a security expert, and Ukiah, a weapons and defense expert; they kept their numbers small to maintain loyalty. The Slams kept meticulous records and multiple ID docs for false identities.
The gang was captured and imprisoned in the Greylands Security Complex on Tentator but managed to escape the poorly-maintained high-security prison. However, after attempting—and failing—to break into a Commerce Guild security vault, the Slams were recaptured in 24 BBY and sent back to the prison. Their ship, an Ubrikkian star yacht, was later confiscated and used by the Jedi in their mission to Romin to track down scientist Jenna Zan Arbor.
Very shortly after their re-committal to the Greylands prison, the Slams again escaped by bribing the prison director. For refuge they fled, of all places, to Romin, where Slam, unwittingly, ran into Jedi Master Obi-Wan Kenobi (who was impersonating Slam) at an extravagant reception for the world's wealthy hosted by the planet's tyrant-dictator Roy Teda. They chatted over quint-berry juice.
The Slams next joined up with Teda and Zan Arbor in their escape from the conflict then erupting on Romin from an uprising of its oppressed citizens led by Joylin. The gang was furious that the Jedi had impersonated them. The Zan Arbor-led criminal elements fled in the Slam's re-secured yacht to the Mid-Rim planet of Falleen, there to join their forces with arch-enemy of the Jedi Order, Granta Omega. The Jedi followed them, however, thanks to a tracking device planted by Kenobi's Padawan, 17-year-old Anakin Skywalker.
Even so, Slam and Valadon were able to evade the Jedi and escape Falleen with Omega and Zan Arbor, traveling to the galactic capital planet of Coruscant to execute a major attack against the Republic. In that attempted Bank of the Core Plaza heist and Senate murder operation (in which Supreme Chancellor Palpatine was targeted), Slam and Valadon were captured again and returned to prison.