Disgaea: Hour of Darkness, developed by Nippon Ichi Software, follows Laharl, a demon prince who wakes after two years of sleep to claim the throne of the Netherworld, in a turn-based strategy game with sharp humor and a character-progression system that allows leveling up far beyond what's usual in the genre. It became a cult title in the West almost immediately.
Its legacy is enormous: it laid the aesthetic and mechanical foundations for an entire line of Nippon Ichi tactics games that kept expanding for years, and it remains, more than two decades later, one of the favorite entry points into the Japanese turn-based strategy genre.
This system doesn't run in the browser yet (Dreamcast, GameCube, PS2 and Xbox are on the way as web emulation matures). The dossier, media and community are already all yours.
If you liked this one