From the introduction:
Untold ages ago, four pairs of powerful demigods — one set tyrannical, one set benevolent — ruled over the four elemental planes. Kelizandri, the evil elemental lord of water, conspired with the villainous lords of air, earth, and fire, to trap the four good elemental lords within arcane gems. One by one, they imprisoned their benevolent counterparts within these artifacts. Ever since, the Garnet Brand, Gasping Pearl, Moaning Diamond, and Untouchable Opal have remained hidden throughout the multiverse, and the residents of the elemental planes now accept the remaining elemental lords’ dominion as part of their existence. Even now, untold millennia later, relatively few know of the existence of the imprisoned demigods.
User summary:
For tier 3 - 7.