The Temple of Sacred Ashes is a location in Dragon Age: Inquisition
It was the site of a Peace Conclave organized by Divine Justinia V
Leaders from the Mages faction and from the Templars faction participated in this conclave, which was an attempt to find peaceful resolution to the Mage-Templar war
However, this peace summit did not end well - a mysterious explosion killed everybody there, including Justinia V, and opened a huge tear in the sky, called the Breach
The Inquisitor was the only one who escaped alive, leading Cassandra to believe that he was responsible for the deaths and the breach.
In the quest The Wrath of Heaven, Cassandra, the Inquisitor, Varric and Solas journey to the temple in order to seal the Breach