God of Hindrance

Zeus' master bolt - the weapon upon which all other lightning bolts are modeled - has been stolen, and Zeus has accused Poseidon of instigating the theft. The Lord of the Sky believes that Poseidon used Percy, a human hero, to steal the bolt in a plot to overthrow Zeus. Zeus has given Poseidon until summer solstice - only ten days - to return the weapon. Poseidon is offended, but he also dreads the thought of war with Zeus. He needs Percy's help to find out what really happened to the bolt. Chiron believes that Hades, Lord of the Underworld, stole the bolt to set his two brothers at each other's throats. Chiron tells Percy that he must travel to the entrance of the Underworld in Los Angeles (by land, since Zeus would blast him out of the sky if he tried to fly), confront Hades, and return the master bolt to Olympus before the solstice passes in order to prevent a war between the gods.

The Goddess of Hearth knew what would happen, if Poseidon actually did plan to overthrow Zeus, a war would breakout between two Gods, and a war between two Gods would lead to chaos. In order to prevent war from happening, she appointed someone to observe Percy Jackson, to see if he was the cause of the master bolt's disappearance.