Powerstones, also called power crystals, are special stones associated with telepathy and mind control, that featured heavily in the design of Snaff's cephalolithopathic golems. They were embedded in golden laurels, and carefully selected to map the activation zones of the laurel wearer's mind.
The grey stones were chosen to repel the mind aura of the Dragonspawn. Before battling the Dragonspawn, all of Destiny's Edge got tattoos reading DE, with the tattoo ink seeded with tiny powerstone chips. In the fight against Morgus Lethe, Snaff and Zojja used red powerstone laurels to control two barques, which were laden with traps for boarding Risen. And in the fight against the Destroyer of Life, Zojja treated Garm's battle armor, Rytlock's gauntlets and Caithe's stiletto with blue (ice) powerstones, as well as Logan's hammer—a trophy of his first kill, a centaur.
In the battle against Kralkatorrik, Snaff used powerstone portals into the Elder Dragon's mind, to help keep it on the ground. They are portals, except that you don't walk through them with your body, but with your mind. The powerstones he used were petrified drops of green blood from Kralkatorrik—blood from his last battle. For thousands of years, Glint had gathered them from the sands of the Crystal Desert and hung them on a tree, keeping them from mortal hands. They were like powerstones, but tied to the life force of Kralkatorrik.
Snaff fashioned a powerstone laurel for Kralkatorrik out of a rib of Big Snaff, and tasked Glint with fastening it about the dragon. Trenches were dug at each entrance to the sanctuary, and filled with enspelled dragon-blood stones, so Zojja could make them embed themselves and Snaff could turn the minions against each other, buying them more time. While Snaff kept Kralkatorrik on the ground, Rytlock could deliver the killing blow with the Dragonsblood Spear that Glint had made out of one of Kralkatorrik's own spines, and the others would hold the entrances. They also packed the blood droplets into exploding arrowheads, and each one that pierced Kralkatorrik's hide filled him with thousands of powerstone fragments. They were salted through him by the time Snaff needed to take over his mind.