Stella Deus takes place in a world called Solum, which is slowly being swallowed by "Miasma", a mist-like substance that destroys all life it touches. Against this creeping apocalypse, several groups have developed responses. The Aeque Church, led by High Priestess Lumena, believes that the Miasma is God's will, sent to bring the world to an end, not with a bang, but a whimper. A warlord, Dignus, has taken to ravaging the countryside with his armies, imposing the law of the jungle: he who will not fight for his life does not to deserve to live. And finally, an alchemist named Viser is using Dignus's patronage to hunt the world's Spirits (polygonal creatures whose nature is unknown), draining their life-force to fuel his alchemic inventions, which he is sure will save the world. His friend and deputy, Spero, is the game's protagonist. Spero must make his way through this muddy political situation and see if he can save Solum.