Ensure the sacrifice effect every turn by sacrificing the Shaman to himself each time and you should be golden
Primeval Titan's ability to search up any land, not just basic lands, from your library and place them directly onto the battlefield allows it to find powerful land effects like Hanweir Battlements, Sunhome, Fortress of the Legion, and Valakut, the Molten Pinnacle
it can give your Grixis Control deck a Combo-Control vibe like a pair of Splinter Twins or a couple of Upheavals (if you grok)
Beyond that go for faster lands Sanctum of Ugin, Ancient Tomb, Eye of Ugin, better ramp Mana Crypt, The One Ring for draw, the Eldrazi Titans (all), Conduit of Ruin, Void Winnower, Portal to Phyrexia, okay I'll stop now
Supply and Demand We all know that the market forces, supply and demand, decide over the price of a certain Magic trading card
It even shares the mana value of Gravedigger, so I get why this card costs this much, even if I would never build around it