They are one of the more primitive warlike peoples who use the Stargate (which they refer to as "the Portal") as a mode of transport to get from planet to planet. They are a collection of various tribes which are differentiated by the tattoo markings on their foreheads. They make use of axes, war clubs, arrows, crossbows, spears, and throwing weapons such as chakrams. Their buildings consist of huts and similar wooden structures.
The Bola Kai are known to leave little of their enemies once they are through with them. Once they have extracted all of the information they can from their prisoners, they are suspected of eating the bodies of their enemies. (SGA: "Missing")
In 2007 after the Athosians are captured by former Wraith Michael Kenmore, the Bola Kai arrive on New Athos for an unknown purpose, possibly to attack the Athosians. The Bola Kai find the settlement empty, but arrive at the same time as Teyla Emmagan and Doctor Jennifer Keller are visiting. The Bola Kai hunt Teyla and Keller and capture Wraith worshipper Nabel Golan who led Michael to the planet. After being rescued by Teyla and Keller, Nabel claims that the Bola Kai are Wraith worshippers and are responsible for the Athosians getting culled by the Wraith. The Bola Kai eventually capture Teyla and Keller and Omal reveals to them that the Bola Kai didn't arrive at New Athos until after the Athosians were gone. Under threat from the Bola Kai, Keller gives them the address to an uninhabited world after being asked where they came from. Teyla and Keller are rescued by Nabel while the Bola Kai are distracted by the arrival of a cloaked Puddle Jumper, but Nabel only wants to know the address to Atlantis. After Nabel is defeated, the Bola Kai surround Teyla and Keller, but Lt. Colonel John Sheppard, Doctor Rodney McKay and Ronon Dex arrive and kill several Bola Kai and drive off the rest. A couple minutes later, the Bola Kai return, but the team is able to escape New Athos safely.
Following the escape from the Bola Kai, Atlantis sends more teams back and discovers the Bola Kai gone, presumably scared off by the deaths they suffered from fighting Sheppard's team. (SGA: "Missing")