Shimmerstone is a unique item dropped by Peat Mummies and the Dreadful Peat Mummy. It can be thrown a relatively far distance by right-clicking it, and will land as a dropped item. This is useful because it will distract Peat Mummies, who actively search for dropped Shimmerstones and consume them, allowing you to get away before they target you again. It has an animated texture.
Shimmerstones can be placed inside Repellers with a right-click, making them function. They can also be removed with a shift right-click.