Bort

Earth Glide. The bort can burrow through nonmagical, unworked earth and stone. While doing so, the bort doesn't disturb the material it moves through.

False Appearance. While the bort remains motionless, it is indistinguishable from a normal rock.

Treasure Sense. The bort can pinpoint, by scent, the location of precious metals and stones, such as coins and gems, within 30 feet of it.

Spellcasting. The bort is a 1st-level spellcaster. Its spellcasting ability is Constitution (spell save DC 12). The bort knows the following spells:

Cantrips (at will): magic stone, mold earth
1st level (2 slots): earth tremor

Slam. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 4 (1d4 + 2) bludgeoning damage.

Mud Trap (recharge on 6):  The bort turns a 10-foot square of ground into a sticky quagmire for 1 minute.  The area becomes difficult terrain. 

When the mud trap appears, each creature standing in its area must succeed on a DC 12 Strength saving throw or become restrained. A creature that enters the area or starts its turn there must also succeed on a Strength saving throw or become restrained. A creature that fails a Strength save to escape the mud trap then has disadvantage on the next Strength save to escape.