Spotting the danger, the complex machine transformed itself to soft sand to let the object pass through.  As soon as it did, Vakama sent an intense blast of flame into the tunnel, so hot and bright it sent Onewa stumbling backwards.
When the Toa of Stone could see clearly again, an incredible sight greeted his eyes.  The Kranau caught mid-transformation by Vakama's fires, had been fused into a statue of glass.

Maze of Shadows, Greg Farshtey, p 34-35