Have you ever played Brutal Legend? If yes, have you heard of Sacrifice? Assuming not, Sacrifice IS one of the first and the best Action RTS hybrid titles out there, so BL's gameplay is hardly all that "innovative" (though still fun). Fun fact: Tim Curry starred in both of those games. You don't know who Tim Curry is? Go sit in the corner, you're on timeout.
Sacrifice is an incredibly bizzare and twisted game. Probably the weirdest I've ever played, aside from American McGee's Alice and The Path. The game sounds fantastic, has got a very memorable soundtrack and the voice acting is simply superb. The world and the creatures that inhabit it are quite strange, but unique and beautiful in their own way. The graphics are pretty outdated in this one though and it's something that may be difficult to overlook, especially if you're having a hard time getting engrossed into the game.
The gameplay is something that takes time to get used to and playing the (rather comprehensive and enjoyable) tutorial is a must here. As previously mentioned, it's a third person squad based game where you make formations out of your units, cast spells to aid them in battle and complete various map objectives. Whatever units and spells you acquire vastly depends on the deities you choose as the story progresses, thus making the game replayable due to the large amount of combinations that can be created.
Last but not least, game has the same oddball sense of humor you might find in titles like Earthworm Jim. Considering that Earthworm Jim was the first successful creation of (now defunct) Shiny Ent. along with Sacrifice that followed a few years later, it's not all that surprising.
This game is really, horribly underrated. But at the same time, it's not for everyone. If you enjoy the hybrid gameplay of games like Brutal Legend, Overlord or Natural Selection (to name a few, but those three are on Steam), you might as well give Sacrifice a chance.