Ra Chak Kai is a female spy serving for the Resistance against the Caste Houses. She posed as a science officer serving for Commander Rado Dar. She was on Commander Dar's spaceship when it crash landed on Earth, in the unsettled territories of the United States. Kai gave the planet's assessment to Commander Dar as being uncharted, in which Commander Dar immediately claimed it as his to rule.
Kai went along with Commander Dar and his surviving soldiers in taking over Earth, effortlessly razing Fort Larrabie in the process, and selecting Silver City as their suitable location in establishing a beacon to contact a House of Dar fleet to retrieve them and reinforce in their conquest. When Dar's forces attack and chased the human inhabitants at Silver City, Kai secretly fled with the humans and came to the Apache camp. She was caught by Zeke in which she was able speak to him in English, stating that she came to help him and his species given she cannot bear to see another race being enslaved by the House of Dar like they did to her own people. Kai warned the humans about the beacon and need to destroy it before it is completed by the next morning.
Kai joined with Zeke, War Hawk in sneaking past into Silver City through the town's abandoned silver mine - as recommended by Alan Cross - and locating a cache of dynamite to be use in destroying the beacon while the rest of the Apaches and American settlers in providing a diversion against Commander Dar. However, Cross actually tricked Kai and her allies as he planned on siding with Commander Dar to sought his own survival and informed about the attack. Kai, Zeke, War Hawk and along with No Name were hunted down by Maw Hunters. The group fled and found a mining shed across a chasm where they expected the dynamites are stored. After disposing the Maw Hunters, they then realized of Cross's treachery upon finding the shed empty. Despite this, Zeke learned of a crate of explosives salvaged from Commander Dar's ship in Silver City and decide use it on the beacon. Kai and the others infiltrate into Silver City but only to be caught by Commander Dar.
By the next morning, Kai and the others were about to be executed via firing squad but fortunately to be saved by the arrival of the Apaches and the settlers. During the battle, Kai grab the explosives and place it on a makeshift catapult to be launch on the beacon. But before she needs to find a counterweight, she was near-fatally shot by Commander Dar. Forcing a grieved Zeke to have a duel with Commander Dar, in which Kai tells Zeke in using his salvaged alien gun to be set on the third setting. Which the weapon fires a bullet which causes to encase Commander Dar in a caulk-like substance, inadvertently causing Commander Dar's body to fell on Kai's catapult and launching the explosives, destroying the beacon with aid from No Name (then officially named as Angry He Throws the Circle). Following the battle, Kai was being treated and shows her and Zeke's affections for each other. As the humans celebrated their victory, Kai discretely contacts the Resistance and reported back that she find humanity as a potential ally in their struggle against the Caste Houses.