Stubborn Boulder

Wondrous item, uncommon

Price: 200-800 gp | high sentimentality

This boulder starts as a rock small enough to fit in a pocket. If you use an action to speak the command word and throw the rock to a point on the ground within 60 feet of you, the rock becomes a giant boulder 5 feet in diameter weighing 4,000 pounds and immune to all damage. The rock harmlessly pushes away creatures occupying its space when it enlarges. Creatures must make a DC 14 Strength check for every attempt to move the boulder, and every success allows them to push it up to 10 feet. On a failure, they must succeed a DC 10 Strength check to keep the boulder in place or it begins moving backward. If the boulder has been moved away from the spot where you threw it, it attempts to roll back to its original spot at a speed of 20 feet using the most direct path possible but moving around immobile obstacles. Creatures must succeed a DC 10 Strength check to stop the boulder from moving. If the boulder moves into another creature’s space, it pushes the creature out of its path and the creature suffers 4d6 bludgeoning damage. The boulder persists until the person who spoke the command word to change the rock into a boulder speaks the command word again to turn the boulder back into a rock.

Paid

The boulder no longer attempts to move around structures, instead running into them, dealing 8d6 bludgeoning damage as long as it remains in contact with the structure.

Overpaid

When you speak the command word, you choose whether the boulder is 5 or 10 feet in diameter, but all its other attributes remain the same.

Source: The Gray Merchant of Asphodel