The Crystal Desert · Temple of the Six Gods, Crystal Sea
Margonites desecrate the Temple of the Six Gods
In their fervor for Abaddon, the Margonites slaughter the priests and deface the statues of the five other gods at the Temple of the Six Gods — an outrage that helps spur the war between Abaddon and his brethren.
On the shores of the Crystal Sea stood the Temple of the Six Gods, a place of homage to Balthazar, Dwayna, Grenth, Lyssa, Melandru and Abaddon. Learning that the gods had revoked the gift of magic against Abaddon's wishes, his Margonite followers traveled to the temple and, in their love for their patron alone, slaughtered the priests of the five gods and defaced their altars, statues and scriptures.
This sacrilege apparently spurred on the conflict between Abaddon and the other gods. The wiki places the act "at some point before the Exodus" without an exact date. When Abaddon later fell, he dragged the defiled temple down into the Realm of Torment with him, where it became known as the Temple of Abaddon.