Sandshark

Sandsharks are thought to be one of the parts that make up the infamous Bulette, with some sort of dragon or elemental (and who knows what else) making up the rest. They exhibit the same behavior as the larger and more fearsome Bulette, “swimming” through loose sand and earth and ambushing prey that walks too close to their burrows, but they are significantly smaller, stupider, and lack the Bulette's magically-hardened shell.
A sandshark is a reptile, generally around the size of a large pony or small horse. Their forelimbs are massively oversized, with enormous shovel-like claws to grip the earth and pull themselves forward through it. Their hindlimbs only look underdeveloped in comparison to the forelimbs; compared to the body they have the same proportions as any other large land-dwelling lizard. The tail is short and weak; it swells with fat if the creature is well fed, but can become nearly skeletal if it is underfed.
Sandsharks survival depends on the earth-magic infused scales that ring their head and shoulders. These scales “attune” the creature to the surrounding earth and sand, allowing it to “swim” through the surrounding strata as if it were a heavy liquid, instead of a packed collection of solid granules. It uses its foreclaws more for traction through this magic-induced psuedo-liquid than to actually dig through it, though observations of sandshark behavior suggest that they do still use these claws for digging holes to store leftover meat or to keep their eggs safe.
A sandshark's jaws are filled with short, ovoid teeth with a single serrated edge down the back of the tooth, perfect for capturing a large creature and dismembering it once it has died. Their hunting tactics revolve around ambush; the beast will lunge from hiding beneath the sand’s surface, bite down on its victim, and then attempt to drag it back below-ground, where suffocation serves to kill it if the beast’s jaws cannot.