I Reincarnated as a Dungeon Core, So I Built a Monster Kingdom [LitRPG, Progression Fantasy, Monster Evolution]

Riven died once. He expected his second life to be different. He just never expected to wake up as a Dungeon Core. Trapped deep beneath the earth with nothing but a strange system and a steadily growing supply of energy, Riven has no body, no allies, and no idea why he was given a second chance. But he does have one advantage. He can create monsters. At first, his creations are weak. A few simple creatures are all he can afford, and every monster costs precious energy. But as his dungeon grows, so does his power. He learns to gather energy, expand his territory, create stronger monsters, and develop abilities that should be impossible for a dungeon. Soon, his dungeon is no longer an empty cave. It becomes a home. His monsters become more than tools. They become companions, soldiers, guardians—and eventually, a family. But growth attracts attention. Adventurers come seeking treasure. Kingdoms begin to notice the strange dungeon appearing in their territory. Powerful monsters lurk beyond his borders, and forces far greater than him are beginning to move. Riven has a choice. Remain hidden and slowly build his strength... Or step beyond the dungeon and create something the world has never seen before. A kingdom where monsters have a place to belong. A kingdom built from nothing. And at its center stands a Dungeon Core who has no intention of dying a second time.