It should come as no great surprise, then, that
Throne of Darkness plays quite similarly to the
Diablo games. It has a few very noticeable changes, which tend to be both exciting and frustrating. In the end the game isn't quite as engrossing as
Diablo II--at least in the long term--but for a while you'll probably find it more appealing, due to the freshness of a number of its ideas.
An evil warlord has taken over the land, and with it just about wiped out the population of the Japanese province you're in. It's up to you, as controller of one of the four clans in the land, to take the countryside back and destroy the influx of evil demons and undead. By the time that you're an hour into the game or so, you will have found all seven samurai that you can control. Each samurai has their strengths and weaknesses--your Brick is a serious tank, so polearms are best for them, whereas your Wizard should have ranged weapons but rely mainly on spells. The classes aren't quite as differentiable as I would have liked, but they're certainly different enough to let you tailor your play style to what you like.
The real difference between Throne of Darkness and the other Diablo-esque games is that you control up to four of the samurai at once. This ends up being both the game's biggest plus and its biggest irritation. Having four of your warriors running around at once can be exciting, and you can switch between them with a simple mouse click or a tap of the space bar.
The problem comes when you start playing with settings and formations. It's non-trivial to get your characters set up the way you want them, and the animal names for the formations, while cute, do little to tell you just what they're going to do. And every single character in the game can use magic, but none of them use it effectively, making a straight brawl much less time-consuming than throwing spells around. It's irritating to have to switch between characters constantly and pick spells to cast, and it's time consuming. What's worse, the formations don't rotate, which means that they're only effective for a particular facing. Ugh. The designation of a 'point man' and basing the formation around them would have been a nice touch, and one that would have made formations considerably more useful.
Still, there's a lot of neat stuff going on in the game. Once you rescue the blacksmith and the priest, you can use them at any time. You can give weapons you don't like to the blacksmith, who will turn them into 'points' that you can use to create new weapons. He can also repair the ones you have. The priest can do the typical priestly things--identification and donating to the gods being the two main ones.
When you tire of the long single-player campaign, you can jump into the multiplayer experience. It's based around beating the Dark Warlord and, effectively, becoming them. Don't think that it's going to be trivial, though--it's probably not too realistic of a game to play over the Internet, unless you have a whole day to set aside. Local LAN games, on the other hand, can have that sort of staying power.