Unleashing the Untouchable

From the introduction: Long before the rise of human civilization on Golarion, eight elemental lords reigned over the Elemental Planes, with a benevolent ruler and vile tyrant vying for supremacy on each of these four planes. The sinister Kelizandri, lord of water, forged a temporary alliance with his three evil counterparts, and together they overpowered each of the good-aligned rulers and sealed them within nearly indestructible gemstones. These they hid far from the Elemental Planes to be guarded by the elemental lords’ servants.