You indicate a location which the device will fly to within the device's range. It will then fly to and hover 40 feet over that location. It will infuse the ground in a 20-foot square around that area with infernal strands, which reach up to grab trespassers in the area.   For the duration of the effect, the terrain effected becomes difficult terrain, and any creature which starts their turn in the area automatically takes 1d6 fire damage.   A creature in the area must succeed a STR saving throw at the beginning of each of their turns or be restrained by the infernal threads. The creature may make a STR ability check with a DC equal to your spell save DC in order to attempt to release themselves from the restraint. On a success, it is freed.