Serious Sam: Siberian Mayhem is a 2022 first-person shooter game developed by Timelock Studio and Croteam, and published by Devolver Digital.

Sam travels the Siberian tundra and forests and finds an abandoned village surrounded by Octanian troops where he meets with One-Eye Olga, a legendary Russian sniper who was believed to have been killed during the storming of the portal in Tunguska.

Olga reveals she faked her death, hiding in an abandoned church in the meantime and was also responsible for shooting down Brands plane.

There he meets Ledov's partisan squad: the stern and dense Ivan, the energetic and militant Natasha, the silent Vlad and the leader of the group himself, the former rock musician Igor.

Ledov tells Sam that there is an abandoned railway depot on the outskirts of the village, where a working locomotive is present which, they can use to reach the closest town Ustinov and travel to Tunguska from there.

Sam and Ledov's partisan squad fight through Kalinovka and reach the depot where they Finally, having beaten off significant enemy resistance, board the train.

Sam suspects something is wrong, and they are subsequently ambushed by Octanian raiders that bomb the town, undermining a nearby building.

General Brand himself, in his monstrous form, suddenly appears, grabs Ivan and tries to convince Sam to join Mental's forces.

With initiative from their team lead Evgeny, they compiled an 80-page design document that they submitted to Croteam in September 2020, just before Serious Sam 4's release.

Croteam consulted Timelock Studio on creative and technical aspects, including optimisation, while Devolver Digital acted as the game's publisher.

[4] The game was first teased via a 34-second video published to YouTube in December 2021, showing protagonist Sam Stone navigating a frozen landscape.

[6] Devolver Digital referenced the video again in early January 2022, stating that it would announce a new Serious Sam entry later that week and release it later that month.