Ustanak was a human-based B.O.W., based on a former employee of Dr. Carla Radames, and was instrumental in Neo Umbrella's hunt for Jake Muller for the creation of the Enhanced C-Virus. Ustanak's name comes from the Serbian word for "revolution".
The individual that became the Ustanak was infected with the C-Virus on June 22, 2011, which he was rather pleased with. The unnamed individual's own writing stated that he had been born with an incredible frail body and had no qualms about losing his humanity if he gained power. A report filed five days later defined the mutant's survival after the first 24 hours as "substantial progress", considering the deaths of the earlier 322 candidates. At some point during the first few days, the individual was involved in a laboratory accident, leading to the loss of its right arm (either through damage caused or subsequent amputation was not stated in the report). Despite the C-Virus' notability for mutating J'avo endlessly, his arm failed to regenerate - an evident flaw. Regardless, his abilities in other fields led the Neo-Umbrella scientists to consider the experiment a success.
On July 2, it was noted in a continuation of the experiment log that the creature - now dubbed "Ustanak" - had the capability of crafting its own weapons, designed for the purpose of grabbing enemies. Orders were subsequently given for the researchers to design an artificial arm to replace the missing limb to increase its performance.
Furthermore, the creature formed a strong emotional bond to his creator, Carla Radames, who he viewed as a goddess for giving him the power he had desired. She was the only one he would listen to, and notes from another Neo-Umbrella member stated that their interactions resembled that of a mother and her child.
By December, work on its new arm involved attachments such as a drill, though orders from Carla Radames specified that an arm (including mechanical hand) needed to be designed, for the purpose of capturing people. Work was problematic, given the researchers' attempts to design a hand that would not appear like a claw from a children's game.
The Ustanak first appeared in Edonia where it was hunting for mercenary Jake Muller who, along with U.S. agent Sherry Birkin, encountered it wiping out a squad of J'avo. The creature began pursuing them, eventually cornering them in an abandoned Warehouse where it was eventually crushed under falling rubble. However, the Ustanak recovered quickly and pursued Jake and Sherry whilst they were traveling in a BSAA helicopter. Although it was assisted by attack choppers piloted by Neo-Umbrella forces, they managed to knock the creature off the helicopter which crashed shortly afterward.
The Ustanak continued hunting for Jake and Sherry, who were trying to escape the mountains. It used Oko B.O.W.s to try to locate them whilst they were navigating through the caverns and a drill attachment on its arm to break through rock walls, but they managed to evade it. After several narrow escapes, the creature managed to trap them but they were able to incapacitate it with a giant mining drill. However, that too failed to kill it and it ambushed Jake and Sherry when they were distracted by a J'avo squad led by Carla Radames. The beast knocked Sherry unconscious and pinned down Jake with its foot, preventing him from escaping while Carla conversed with him about his father and his unique blood. As the J'avo moved in to capture them, the Ustanak violently stomped on Jake's face, rendering him unconscious. Jake and Sherry were then taken to a Research Facility in China by Neo-Umbrella. After they managed to escape the Facility, the Ustanak was again sent to hunt them down.
While in China, the Ustanak found Jake and Sherry again, this time in the company of government agents Leon S. Kennedy and Helena Harper. Still looking to capture Jake, the Ustanak was forced to face off against the four of them, however, they proved to be more than a match for the creature. The Ustanak tried to separate the party and eliminate them one by one, but this strategy failed and the beast was eventually badly weakened by gunfire. The battle with the Ustanak ended when an electric pylon toppled onto the monster, allowing the party to go their separate ways. However, the ever durable Ustanak survived the blow and retreated from the crash site. Jake and Sherry were eventually re-captured by J'avo working for Carla Radames and they were taken to Neo Umbrella's underwater facility. The Ustanak was presumably sent to the facility to ensure that they didn't escape again. The remaining Neo Umbrella was worried about what to do with him since the only person he would listen to had been killed by that point, but knew he'd stay focused on his previous orders concerning Jake Muller. One member noted that Ustanak was exuding a feeling of sadness and was perhaps somehow aware that Carla had died.
When Jake and Sherry were about to leave the aquatic base, the Ustanak appeared again, determined to exact revenge on the two for its previous defeat. Jake and Sherry became frustrated with the creature's persistence and they prepared for the final battle. Although Jake succeeded in tearing off the creature's mechanical arm, the Ustanak kicked Sherry onto a platform, causing her to lose her gun to a smelting pool. Determined to finish off Jake, the beast trapped him on a narrow gantry and kicked his gun into the pool, forcing him to engage in hand-to-hand combat with the Ustanak. However, Jake's abilities enabled him to counter the Ustanak's blows and eventually sent the creature into the pool with a devastating punch to the face. Believing that the Ustanak was finally dead, Jake and Sherry attempted to leave the aquatic base using a cargo platform.
Unfortunately, the Ustanak, badly burnt but still alive, made a final attempt to eliminate them by jumping aboard the platform. In response, they started dropping objects to knock off the creature but that only managed to slow it temporarily and it leaped to the front of the platform, destroying a crate of weapons. Noticing an Elephant Killer magnum lying on the ground, Sherry crawled to it as the Ustanak raised its arm to deliver the final blow. She managed to grab the gun but could not steady her aim, so Jake grabbed her hand, allowing Sherry to shoot the Ustanak's exposed heart. The beast tried to make the last attack but collapsed before it could strike and finally perished from its wounds. The Ustanak's corpse fell off the platform and was completely incinerated by the inferno.