The article uses Przybyszewski’s writing as a litmus paper for testing different incarnations of „the Satan of modernity” – civilizational developments, pathologies and ideologies. Blasfemies and demonomanias express internal psychomachia of the era, torn between fading sacrality and nihilistic currents undermining its foundations. Partially Satanist, partially Gnostic phantasmata and the figure of satan can be treated as a defence against nihilism and anarchism, against the metaphysical void of the „world without God”. The author also traces „the Satan of modernity” in the individual consumed by demonic power of unconsciousness, hubris, fear and madness, as well as insanity of the body and soul (demons of gender and art). Works of Przybyszewski can be viewed as an interesting documentation of catastrophical „collective insanity”, suggesting, that the mankind is flawed with ontic and anthropological „pathology” and life itself is insanity