SiMo, a robot designed to aid the Core Guardians, is the fourth character. Haigen Hawkins is a former Brightholme slum dweller who somehow managed to make it to Elysion-1 and join the military.

Skye Autumn, the player character of the first game and Sweet Autumn, Skye's younger sister both follow on from their father, who was killed in action. The player takes control of one of four Core Guardians in the game, and it is shown they travel together as a squad. The war between Britech and the Lumes has been going on and off for an indeterminate amount of time. To counter the Lumes, the Britech Foundation has created and armed a military wing known as the Core Guardians, who are tasked to defend the Cores using their arsenal of weapons and defensive towers. If successful, the area will become swamped with poisonous spores. The Lumes, which are hostile to Cores, propagate large plant-like access shafts until they are close to a Core, and then launch a coordinated attack on the Core until it is destroyed. They convert inert gases like nitrogen into oxygen, and cleanse areas of toxic mushroom-like spores native to Loek-III, which are linked to Lume activity. Key to the colonies' survival are Cores, which appear as large blue spheres of energy.

Tsygan is a minority compared to the «Brightsiders» – those who side with Britech. It is hinted that some settlers still survive in the ruins of Brightholme and are part of an obscure organisation known as Tsygan, which is opposed to the vast, almost governmental power that Britech holds. A previous arboreal settlement, Brightholme, had been set up in the wilderness but had collapsed from repeated attacks by the Lumes, a race of diverse creatures native to the planet. Sanctum 2 takes place in the future on the planet Loek-III where a major human colony has been established by the Britech Foundation in the city of Elysion-1, a vast elegant metropolis.

The successor to Sanctum, Sanctum 2 was announced in 2012 and released on. Sanctum 2 Download Free Full Game is a first-person shooter tower defense video game, developed by independent developer Coffee Stain Studios for Microsoft Windows, OS X, Linux, PlayStation 3 and Xbox 360.

Sanctum download free