A lost chapter in the Serious Sam series
Serious Sam: Siberian Mayhem is a stand-alone expansion built by Croteam together with Timelock Studio. It follows Sam Stone as he pushes through the wild lands of Russia to catch up with the traitorous General Brand, who stays one step ahead at every turn. The trip runs across five new levels, from Arctic coastlines and desolate forests to abandoned villages and a ghost town. Along the way you get forgotten stories, unexplored places, and the series' usual guns-blazing battles against Mental's Horde. The world is large and open enough to wander and fight in for as long as you want.
Fighting the Horde with friends
The game carries an Online Co-op feature, so you and your friends can take on the Horde together over the internet. Expect big open spaces where enemies come at you from all sides, which means covering ground as a group and keeping each other standing when the screen fills up. Alongside the main push toward Tunguska, side-missions open up extra chronicles tied to these lands, giving a group more to do once the main road is done. The world also hides useful, silly and weird secrets scattered across the map, so splitting up to poke around pays off.
Weapons, vehicles and new enemies
Sam's arsenal grows here. You get new weapons including the legendary AK and the experimental Perun crossbow, plus new gadgets and vehicles for when you want firepower from above or something with serious weight behind it. Mental sends a fresh set of foes and bosses at you, some of the most advanced and intimidating creatures in the Horde, so old habits from earlier games will not carry you far. New outcasts and unexpected characters show up to help Sam on his journey, and paying attention to your surroundings can turn up things the world itself tells you.
Before you start
This is a linear first-person shooter with a dark, atmospheric tone and demons, horror and fantasy mixed into the sci-fi setting. It is a stand-alone expansion, so it stands on its own inside the world of the classic series rather than needing the rest of it. The five levels are big and cold, and Siberia stays unpredictable enough that even the alien invaders feel lost, so expect long stretches of running and exploring between the fights.