"Free me. Free me and my power will be yours." - Thera
God of War:Ghost of Sparta
Thera was a lava titan chained inside the volcano to hold under Atlantis. There Kratos meets with the titan, who according to Thera, his arrival was foretold by Gaia. Thera pleads to be released and for Kratos to acquire his power for without it, they would've both remained prisoners of their own torments. Kratos then hurled his blades on Thera's chest pulling and ripping it open. By doing this Kratos received Thera's Bane and released him from the chains that held him. This caused Thera to break himself free and release his hold from the mountain, which caused the whole place to crumble and led to the eruption of the volcano, and the destruction of Atlantis.
The name Thera is actually the name of Santorini volcano which is to say that the eruption had destroyed the Minoan civilization,which according to some researchers,would have been even Atlantis described by Plato.