After Leveling Up Alone, I Came Back as a Tentacle Monster

After transmigrating to another world, he discovers that he has one soul and two bodies: one male, one female, an older brother and a younger sister, sharing both glory and ruin. One day, his male body is offered up as a child sacrifice to an Old God. To survive, he touches a forbidden curse and becomes an avatar of an Old God. He narrowly escapes death, but is forever transformed into a filthy, evil tentacled monster. It secretly crawls out of the altar and spends over a decade fighting and devouring, living as a terrifying monster until it becomes another dreadful being. It witnesses everything that happens in the city called Saint Paul. It once pitied those poor people, once believed that, as someone from a civilized world, it should uphold morality and righteousness, and even felt sorry for those ignorant fools. More than a decade later, its female body has grown ever more beautiful, but the same tragic fate befalls it once again. The city officials have designated its female self as the next sacrifice, to be offered to the monster in the deep pool. And on that very day, the creature that has been biding its time for over a decade bares its fangs. It will rip those sly, greedy, cowardly poor commoners to shreds. It will make those haughty, selfish, arrogant nobles who fear death suffer the same terror it once endured. Those shameless wretches will only bring more harm to people if they stay alive!