Chesty cast charm monster on it and it failed its save.
According to Chesty:
This animal/demon was like a very broad bull, maybe a head taller then myself at the shoulder. The front of which had a tapered snout that opened like a hinge so that the entire front end was all mouth and teeth. A orifice wide enough one could lie into it and have room both above your head and below your feet. It dived into the earth like one might see a duck or muskrat dive into water, making a furrow of land appear on the surface as it “swam” towards the giant ant creature eating one of my lead horses. It seemed to “swim” through the Earth. If it had eyes I did not see them.