Sacrifice is a game that is old, but still looks good and is perfectly playable, even online.
It is a third person perspective... RTS game :)
You play as a sorcerer who can summon creatures, order them to follow, move, attack, etc.
Your units are very unique and the best part is, they are given to you by the gods, that give you certain missions.
If you work against certain gods, you can forget about their units, but you get others instead.
And they don't behave the same, they have different skills... You can often alternate or even redeem yourself in the eyes of angered gods, which allows for a very replayable game.
The resources for summons are souls, which can be re-used for your creatures, or captured, for enemy creatures.
The AI are good, that makes the game hard. Very, very hard :)
Plus, the voice acting is kind of legendary in this game. There really is no urge to skip the lines of the gods, they are fantastic :) I played the game some time ago, but it seems like Steam version works, but doesn't offer full HD. My version had it, possibly a third party patch?
I highly recommend this game.