I'm looking for a harem fantasy novel where the protagonist aims to build a powerful supernatural legacy.

If you're seeking a harem fantasy novel with a focus on building a supernatural legacy and becoming overpowered, "Demonic Witches Harem: Having Descendants Make Me Overpowered!" sounds like exactly what you're looking for. The title itself clearly indicates the core premise: a harem setting combined with the goal of gaining power through descendants. This implies a narrative where the protagonist not only forms relationships but also actively works towards establishing a lineage that contributes to his overall strength and dominance.

The "demonic witches" aspect suggests a supernatural or magical element to the harem members, adding an intriguing layer to the relationships and potential conflicts. The core idea of "having descendants make me overpowered" is a unique twist on the typical power-up trope, suggesting a long-term strategy for growth and influence within the story's world. This kind of novel often appeals to readers who enjoy the wish-fulfillment aspect of powerful protagonists and intricate relationship dynamics within a fantasy context. The emphasis on legacy building also suggests that the story might explore themes of family, inheritance, and the lasting impact of the protagonist's actions.