Gray stones are a special type of rune you can place on the board. Unlike other runes, these can be placed anywhere you want. The best spot to fit this type of rune would be if there is a space that is still lead and no rune can fit. When the next level starts, you are given a gray stone and you can put it anywhere on the board. As the levels progress and get harder and harder, the chance of getting a gray stone will be smaller.
- In the hint dialog box, this rune is known as a four way piece.