A very beautiful and rich game. The world has a great breadth and depth to it, with historical scenario games you can play to encounter its development first-hand. There are many and varied leaders, factions, and spells that a player can use.
As a 4X game, it definitely leans toward a war game in the 4X format. Combat is frequent, although whether the major players fight one another can depend on your fellow human players if playing in multi-player. You can play through each battle manually, or you can have the computer fight your battles for you. Should a computer battle go badly, you can always redo manually (at least in one-player). When playing one-player, most scenarios and set-ups will inevitably find you at odds with at least one other major player. The scenarios tend to go full-on knock-down drag-out pretty quick, and some can be over quickly should a player play boldly from the start.
An interesting aspect of the game are the layers. There are above-ground and below-ground layers that a player can transit between, and mostly can settle in both. In some worlds, there is a third layer that does not directly correspond to the other two geographically, but is purposefully much more disjointed and random.
The UI is pretty good, but there are some hitches and glitches. Mostly a player will right-click to activate or execute something, but if you are excavating underground, you have to left-click on a shovel icon on the territory adjacent to your excavating unit. The whole idea is a little vague, so your first time, you may find it frustrating. Giving a stack of units orders to travel long-distance can also get you in trouble, as a blocking unit from another player will cause your stack to re-route, but as soon as that blocking unit is out of sight, your stack will try to go the first way, only to re-route again. Likewise, the combination of all three layers, when present, can make for some very complex routes.
Some scenarios seem designed to trip you up from the start, for instance, by putting you in a position where you either have no money or mana. When you run out of either one, game play is significantly less rewarding, because there is just not much you can do as a player. Keep an eye on your vital stats, of course you need everything, but money and mana drive play turn-by-turn. Stability in cities is important too, but it can slide a little for a while without preventing you from normal gameplay.
If you really want to enjoy the breathtaking breadth and depth of the game, you will want to acquire all of the expansions eventually. Look for sales, it would be mighty pricey buying everything at list price. There is also a mod community, and some of the mods are interesting, though keep an eye on compatibility. A mod that worked yesterday may blow up your game today.
I would highly recommend this for 4X fans, especially if you don't mind a lot of fighting. The magic provides an alternative to the technology research found in many other non-fantasy 4X games, and the sheer variety of creatures, effects, magic items, spells, etc., guarantee some spice in your game play. And dragons. There are dragons.
