Disgaea 4: A Promise Unforgotten follows the story of former tyrant Overlord Valvatores, a vampire who has sworn not to drink blood for 400 years, now leading a rebel group against the Netherworld President. The political setting is the main focus of the game's storyline.
The gameplay features from the previous Disgaea games are still present, but new elements have been added. Players can "grab" party characters in a tower formation and throw them to reach otherwise out-of-reach places. Special abilities like team attacks can be used while in tower formation. Party monsters can still use Magichange to turn into weapons, and they can now fuse together with Demon Fuse to create giant versions of the combined monsters.
The game's hub, Hades, can be customized to the player's liking. Characters found on Valvatores' captured land can be befriended and captured. A captured character can be disciplined and then used to find treasure, added to the party or released. Another feature is the ability to create a custom pirate ship to reverse-pirate Item Worlds.