mysterious giant octopus in dark tunnel

octopus giant dark tunnel mysterious horror fantasy creepy underwater tentacles surreal strange ominous eerie unsettling aquatic creature monster deep sea scifi shadowy depths otherworldly entity enigmatic abyss foreboding passage eldritch abyssal leviathan sinister squid nightmarish behemoth preternatural predator unfathomable enigma primordial terror cryptic colossus ai generative generated synthography