When a hunter reaches level 100, they can to reset to level 1 with a Reincarnation mark. This increases their base stats and unlocks higher difficulty levels. Reincarnation requires time to complete.
Your town economy runs on a circular ecosystem: Hunters sell monster loot to your storage, you use that loot to craft items, and you sell those items back to the Hunters for gold. Essential Infrastructures Evil Hunter Tycoon Wiki