The Fane of The Eye
The writings of Marlos Urnrayle spoke of Marlos traveling to The Fane of The Eye. And there he found a powerful magic item called Ironfang, a war pick that was imbued with the magic of a holy implement of earth power.
The Eye referenced here could have something to do with the floating disembodied eye The Four saw back in Lance Rock after battling the evil necromancer, The Lord of Lance Rock. The 4 witnessed the floating eye above an altar before it faded away. There we found all the cult symbols on the tapestry not just one of the elements. Its makes Templeton wonder if there is some overarching force representing all the elements. If so the The Fane of The Eye might be the heart of what is going on.
After speaking with The Dark Lady, Templeton learned that the Fane was an ancient drow temple dedicated to the Elder Elemental Eye and built by Vizeran Devir. He crafted 4 elemental weapons that he placed there but were taken by the elemental prophets.