Kjallak was a varl warrior who fought in the Second Great War against the dredge. The old varl Torstein eventually took him under his wing as his kendr, along with Olaf and Ulfvalgr, teaching them how to read, fight and survive. Kjallak was however later exiled by him due to his dishonorable ways and, he decided to go to the plains of Valkajokull, going further than any varl had ever been. There, he came to believe that the dredge who resided in the region would invade again.
After moving to Strand, Kjallak eventually joined the criminal gang called the "Mársmidr" and became its lieutenant. He however started desiring to grab more power, directing other members about what to do and dealing with anyone crossing him, without the permission of his boss Freystein, who soon tried to take back control. Kjallak murder edhim about a year and a half before the Third Great War, and started pretending that he was still alive in order to hide his own role. Some of the Governor's Guardsmen who were meanwhile searching into Freystein's disappearance were killed by him.
Later, Kjallak decided to ally with Nikolas and the Magnus twins, leaders of the Aetla Hilmir and Vak'auga gangs respectively, in order to take over Strand and having them assist him in taking over the throne of the varls in Grofheim, so he could lead them in war against the dredge. Nikolas' mender mother Melkorka, who was also an advisor to the Governor of Strand, also joined in. As part of his plan, he had the Vak'auga smuggle in varl skeletons, so he he could use the divine amulet called the "Gift of Hadrborg" to fool the varl warlord Vilmundr into believing he could resurrect the dead varl.
About four months before the Third Great War, Kjallak decided to steal the "Gift of Hadrborg", which was reputed to be able to resurrect the dead varl, and which was given by Torstein to Olaf and Ulfvalgr. His lieutenant Ottar sent his subordinate Johan along with two other men to steal the half of it possessed by Olaf, and Johan succeeded. but started blackmailing his gang into forgiving his brother Hallvard, who had been forced to flee after stealing their profits. He was soon slain by Skoegir, who acquired the half of the amulet he had for Kjallak.
Kjallak also sent Ottar after Ulfvalgr, who he believed possessed the other half of the Gift of Hadrborg, but they failed to find anything as they were unaware that he he never possessed it. When Olaf and Ulfvalgr arrived went to Strand with the boy Stefnir about two months before the Third Great War, Kjallak decided to trap them and met Olaf in Strand's market district when he was trying to get food for his group, offering to help them against Freystein, whom they believed was the one after the amulet, and invited them to The Shattered Shield.
Olaf and his allies took Kjallak's bait, and went to the mead hall after being invited. Kjallak showed them his hospitality and claimed he had often heard about Freystein and his desire to take the Gift of Hadrborg. When Ulfvalgr stated that he wanted to kill Freystein, Skoegir, who was in the room too, laughed at it. Kjallak introduced him and apologized for his behavior, stating he had a strange sense of morbid humor. As Olaf asked him how they knew each other, Kjallak replied that they worked in the same line of business, and he was one of the few people who knew where Freystein might be.
When uUlfvalgr again expressed his desire to kill Freystein and called him a man, Skoegir stated that he wasn't a man at all. The meaning of these words soon dawned upon Olaf's group and the varl soon asked Kjallak if he was working with Freystein. As the Mársmidr trapped his preys, Kjallak revealed that he had killed Freystein a while ago and had taken over his gang, while pretending to be him. The Governor's Guardsmen Eirik and Valgard, who had been following them since they entered Strand and were spying on them all from an opposite building, crashed into Kjallak before he could strike at the varls and Stefnir with his war hammer, causing him to stumble while Eirik's axe grazed his back. Kjallak then tried to strike at the the guardsmen with his hammer, but instead ended up getting it stuck in a wall. His targets were soon able to escape with the help of the two.
A spy soon informed Kjallak that Eirik and Valgard had been following his targets with Hallvard, who was sent to follow them by Ottar. Kjallak in anger decided to punish him for his failure and took one of his ring fingers, before telling Skoegir to inform the Magnus twins and Nikolas about what had happened in order to obtain their assistance, and later go to the Vak'auga's warehouse at the western docks to make sure their latest shipment wasn't delayed.
Nikolas later offered to lead the Aetla Hilmir in capturing Olaf and Ulfvalgr at the Great Hall, and was given permission for it by Kjallak and the Magnus brothers. The attempt however failed as Eirik foiled their plan again. Eirik later learnt about the alliance of the gangs from the turncoat Vak'auga spymaster Leiknir, and was directed to the Vak'auga warehouse at the western docks. There, he and his allies found a varl skull and Hallvard, who had been captured after trying to expose the Mársmidr in revenge for killing Johan.
After discovering that Kjallak was smuggling varl skeletons into Strand and was after the amulet Olaf and Ulfvalgr had, Eirik decided to organize a tournament in order to lure one of the lieutenants of the triumvirate by getting the two varls out in the open, knowing the gangs would send someone they trusted. He also told Runa, who worked for Leiknir, to have the Vak'auga spymaster inform Magnus about it very late, so the Mársmidr and the Vak'auga would struggle to find anyone for the fight. The plan succeeded as they captured Ottar, and forced him to tell them about Magnus smuggling in goods for Kjallak at the Ninth Pier, which he stated would be their best bet to capture the two leaders.
Eirik and his allies however failed to capture anyone at the Ninth Pier and soon found out that Magnus was actually the disguise of two twins of the same name. Stefnir and Runa were also captured by Skoegir after unsuccessfully trying to apprehend one of the Magnus twins, and taken to a warehouse. Kjallak arrived there and demanded to know where the other half of the Gift of Hadrborg was. As he described it in detail, Skoegir realized it was on Stefnir the entire time and gave it to his boss. Knowing that Ulfvalgr would never give it to him, Kjallak mockingly asked Stefnir if it was Olaf, but the boy asked why he wanted the amulet so bad. Kjallak stated that he wouldn't understand even if he told him, and gave the captured Leiknir to Nikolas, as his betrayal had nearly decimated his gang. Nikolas however let the Magnus twins kill him instead.
As the Magnus twins demanded Runa back, Kjallak stated that they first needed to finish meeting Vilmundr and would decide the fate of their captives later. He then went to the temple of Hadrborg in northern Strand with Nikolas and Melkorka, in order to host Vilmundr. After the varl warlord arrived there as sxheduled, he demanded to see the Gift of Hadrborg, not trusting Kjllak due to his guile. Kjallak then showed him a tower shield crafted from a strange metal, with the amulet embedded in it, and Vilmundr confirmed it was true. When the warlord relented that it could not work anymore since Hadrborg was dead, Kjallak pretended to perform a ritual with Melkorka in order to fool him into believing that he could resurrect the dead varl using it, with his men making the skeletons move using stilts and various contraptions.
Soon after convincing Vilmundr, Kjallak was informed that Eirik and his allies had found their way to the temple, and he told the others they needed to leave. The escaped Stefnir however exposed his ruse by jumping on one of the varl skeletons before the triumvirate could flee, and revealed the men inside making them move. He then tried to grab Kjalllak's tower shield, and stabbed his wrist when he tried to hold on to it as expected. Kjallak tried killing Stefnir in rage, but stopped cold as Eirik and his allies burst into the prayer hall.
As Kjallak wrestled with Stefnir, the temple was set on fire from the spell of Melkorka, who was trying to kill Eirik in revenge for fatally wounding Nikolas. Kjallak told Stefnir that what he was doing was for the good of everyone, since the "darkness" would be coming from the north again soon, and Ulfvalgr rescued Stefnir before he was trapped in the fire with Kjallak. Kjallak was overjoyed at retrieving the Gift of Hadrborg, but soon found himself surrounded by flames with no way out.
As Eirik and his allies were unable to find a way to save the Gift of Hadrborg, Ulfvalgr jumped through the flames and wrestled the tower shield containing the amulet away from Kjallak, before tossing it to Olaf. He then fought Kjallak while the two were engulfed by flames, in order to ensure the safety of his allies. The City Watch of Strand under Valgard soon arrived there and arrested the surviving triumvirate gang members. Stefnir however wondered what he had warned him about, before Runa told him to let it go.
The City Watch later found the ashes of Kjallak and Ulfvalgr while searching the temple of Hadrborg and handed them over to Olaf, who decided to lay them both to rest with honor in the territory of the varls. Eirik wondered about Kjallak's warning to Stefnir, which he knew was about the dredge invading again, and asked Olaf about it before he left Strand. Olaf however stated that he was not sure if he was truthful, but expressed confidence that the alliance of humans and varls would be able to repel them.