Storm Spirit

Storm Spirits (Anemoi Thuellai in Greek and Venti in Latin) are creatures of chaos that Aeolus keeps locked away in the hollows of his island. They were created when Typhon was defeated by Zeus and later Poseidon. They serve Gaea in The Heroes of Olympus series.

The Lost Hero
Dylan is a storm spirit sent to kill Jason Grace, Leo Valdez, and Piper McLean. He proceeds by calling forth two more of his brothers. All three of them then proceed to attack the young demigods and the satyr, Coach Hedge, in the name of a mysterious mistress. Two of them are killed by Jason but Dylan escapes taking Coach Hedge as captive.

Later, Jason, Leo, and Piper visit Medea's mall where they find the storm spirits, a captive Hedge, and that she helped kill Leo's mom years earlier. In order to see Aeolus and convince him to help them, Jason, Leo and Piper capture the spirits to present to him. When they finally arrive at his island, the wind master has them imprisoned before releasing the spirits to kill them on Gaea's orders.

Later on, at the Wolf House, they ambush the demigods under the command of Khione. Jason tames one of them, names it Tempest, and uses its power to dispel all the others. Somehow, it managed to survive Hera's burst of energy when she revealed her divine form though it is unknown where it went.

Abilities
In addition to their inherent immortality, storm spirits possess the following abilities:
 * Control over lightning and wind.
 * Power of intangibility
 * The ability to fly at the speed of wind.
 * Multiple storm spirits can merge to form a larger, singular one.

Appearance
Storm spirits have two forms. Whichever one they take depends on how chaotic they are. They can appear as either horse or human-like beings.

Notable Storm Spirits

 * Dylan
 * Tempest

Trivia

 * Storm spirits are also under the control of the Anemoi or wind gods.