Uurg, Spawn of Turg

The self-milling clock here is what makes the design interesting: the upkeep surveil quietly feeds the graveyard that sets Uurg's power, so the creature grows by doing the same thing that fills its own fuel tank. A */5 body means the toughness is fixed and defensive while the power scales entirely off land cards you have managed to bin, which turns dredge-style self-mill, fetch effects, and dual-face cards into combat math. The sacrifice ability closes the loop from the other side: it drains lands out of play to gain life, which is both a slow attrition tool and, less obviously, a way to keep dumping lands into the yard from the battlefield rather than only from the top of the library. That interplay between filling the graveyard and cashing lands for life is the whole strategic axis, and it points at a build that wants to treat lands as a resource you are constantly cycling through rather than hoarding. Green-black has circled this kind of graveyard-as-battlefield frog before, but the surveil-plus-sacrifice framing gives it a self-sustaining texture that most "power equals cards in graveyard" bodies lack, since they usually depend on an external mill engine to do the counting.