It's a highly volatile game - reminiscent of Aristocrat's 50 Lions and WMS Gaming's Zeus in that the only way to get a big win is with the stacked Indians or the "Dream Catcher" wilds. The free spin feature adds extra stacked wilds to each reel and is triggered by 3 Eagle symbols on reels 2, 3 and 4. Indian Spirit's eagle actually sounds uncannily similar to the eagle featured in the Buffalo slot (Aristocrat) which you hear a lot when you walk through Vegas casinos Clearly, it's the right noise (never having heard one myself in the wild!).
Aside from the other Novomatic slots mentioned above, if you like the Gaminator slots then there are several more here on the Games & Fruit Machines site. Check out the very popular European games like Sizzling Hot and Lucky Lady's Charm, the latter having one of the highest RTP's of any online slot at just over 97% (most are around 95% including Indian Spirit which is set to 95.34%).