Battle of Mount Othrys

The Battle of Mount Othrys was the final engagement in the Roman side of the Second Titan War, at the same time as the Battle of Manhattan. The Roman demigods, commanded by Jason Grace, assailed the Titan fortress of Mount Othrys, confronting an army of Scythian dracanae and the titan Krios.

The Lost Hero
The battle was a decisive victory for the demigods; Jason claimed that he "toppled the black throne of Kronos, and destroyed the Titan Krios with my own hands." While Titans are immortal and thus cannot be completely destroyed, presumably, Krios' physical body was destroyed and his essence returned to Tartarus. Jason had also remembered flashes of the battle: a giant in starry armor and a helm mounted with ram's horns. He remembered his army of demigods scaling Mount Tam, fighting through hordes of snake monsters. At the end of The Last Olympian, Mount Othrys was said to have "crumbled into ruins", which at the time was considered to be a natural effect of Kronos' defeat in the Battle of Manhattan, but it was revealed in The Lost Hero by Jason that the Roman camp actually accomplished the feat.