A seriously underrated, overlooked game.
It's set in a made-up fantasy world, in which the king of this main continent has just been assassinated, and replaced with his head general, who has assumed control of the throne. Basically, six different kingdoms and rulers are vying for control of the throne, each for his or her own reasons, and you get to chose and play through one of them. The leaders are all very different in their interactions with one another, come with their own strengths and weaknesses, their own set of subordinate generals and subsequent monsters.
The gameplay is quite solid, being a mix between an RTS game and turned based strategy RPG. On the world map you go through an organizational phase in which you can perform all kinds of logistical actions, and then an action phase, where you decide if you're going to attack one or more cities during that turn, and finally a battle phase where these actions, and those of other countries are carried out. Whether you're attacking or defending you choose three generals (Who have monsters under their command) to battle with, and then go at it. From that point on, it resembles Final Fantasy Tactics or any other turn based RPG.
The generals are fun to gain experience with and level up, gaining extreme powers as you make your way through the game, but the really cool part is the monsters. As your monsters level up from 1-30, they can change/evolve into other, nastier things at level 10, 20, and 30. A regular dragon, for instance, can become a huge, flying beast that can tear through armies, some things even more exciting than that. Still others require strange items to start their changes, and there's lot to be explored and done there.
The challenge comes in knowing how to form armies well, to choose units that compliment each other well, and to know how to keep your monsters alive long enough to become an unstoppable force.
My only complaint about the game is that the map could have been slightly bigger, allowing for longer campaigns. However, it has good re-playability, as each side tells a very different story, despite the fact that combat is pretty much the same from every view point.
This game got pretty harsh reviews, I think it may have just been too close to similar titles like the aforementioned Final Fantasy Tactics, or other big name titles, but it really is a great game that you should check out if you still have the appropriate system, and can find it.