It feels silly describing the story of
Disgaea DS because the story
IS silly. The main character is young boy named Laharl who has been asleep for over 2 years. While he was asleep his dad, the Overlord of the Netherworld, died and he became the new heir. Etna was sent to awaken Laharl and help him claim his throne as the one, true Overlord. Along the way, they meet fallen angels, zombies, ghouls, robots, cartoon heroes, and an evil demon who is actually quite a charming gentleman. All part of being the Prince, I suppose.
Most of the game is spent in battle. Disgaea DS is a very traditional turn-based game with one exception. The game wants you to cheat. That's right... cheat. Learning how to exploit even the most basic function is essential to victory. For example, moving character A next to character B while he is attacking initiates a team attack combo. As long as you don't assign character A any commands, you can always reset his actions after the attack to move him somewhere else. This is just one of the smaller exploits that can be found in the game.
The geo-panels are a major system for the battles too. All of the tiled squares can be changed to a different color that may hold a certain status effect or boost. The source of the tiles' powers come from geo-prisms that are littered all across the map. If you move the prism onto a different color, that new color will have the prism's effect for every other tile. If you destroy said prism however, then every same colored tile explodes and causes damage to anyone unlucky enough to be standing on top of it.
A large chunk of Disgaea DS is invested in the leveling up system. Every character you acquire can be leveled up as high as you like. At any moment, (after requesting permission from the Dark Assembly,) you can re-incarnate a character and keep the skill proficiency and abilities and start over from level 1 to increase their base stats. At this point, you can let loose and create some truly brutal characters. There are around a hundred classes to choose from and plenty of monster type classes as well. Your army will never be puny if you don't want it to be.
The most popular aspect from the Disgaea series is the Item World. Basically, you can travel inside of any piece of equipment you own to level up the properties of that item. It gets much more complex as you go further, but every item has a randomly generated 100 level dungeon inside of it. This is a great place to take your army for power leveling and if you are lucky enough to get an invincibility geo-panel, even skip a few levels if you play the cards right.
NIS didn't want Disgaea DS to be just a quick and dirty port. It has several front end User Interface tweaks to accommodate the DS' capabilities. But the main bonus is that Etna Mode and two new unlockable characters are included this time around. Etna Mode poses the question: "What if Etna killed Laharl at the beginning of the game and became the main character?" While it is slightly shorter than the main game, it is just as funny, if not funnier, at certain moments.