Great Stirring

The Great Stirring is an awakening of all the very powerful Monsters: monsters that had been sleeping, dead or have been in hiding for centuries, to a point where even the gods begin to forget about them. It started in The Titan's Curse and progressed until The Last Olympian. It was caused by the Titans rise in power, culminating in the resurrection of Kronos. Kronos convinced his old allies that had been in hiding and several minor gods to join his cause and wage war on the Olympians. The Olympians eventually won the war, but the damage caused by it caused Gaea to reawaken from her long sleep. In The Lost Hero, it was stated that Zeus thought that if the gods cut themselves off from their demigod children and the world, Gaea would fall back asleep, but apparently it didn't, since Gaea and the Giants were awoken as results of the Great Stirring as well and in turn, they stirred up even more monsters.

Awakened Immortals and Monsters

 * Typhon
 * The Ophiotaurus
 * Kampê
 * Drakons
 * The Clazmonian Sow
 * Tammi, Kelli, and an other unnamed Empousai (according to Chiron)
 * Hyperborean giants
 * Nemean lion
 * Manticore
 * Giants
 * Erymanthian Boar
 * various Triple G Ranch monsters
 * Gaea
 * Various Sea Monsters
 * Orthus
 * Geryon
 * Briares
 * Eurytion
 * Telekhine
 * Cancer
 * Ventus
 * ladon
 * Hesperides