Otrera

"Why should Amazons follow Jupiter, that foolish king of Olympus, when we can follow a queen?"

- Otrera, in The Son of Neptune

Otrera was a Greek demigod daughter, and consort of Ares, as well as the founder and first Queen of the Amazons, and is the mother of Hippolyta, Antiope, Melanippe, and Penthesilea.

History
Otrera was sometimes considered the founder of the Temple of Artemis in Ephesus, which was closely connected with Amazons. She was also sometimes considered the founder of the Amazon nation, though many myths place the first Amazons much earlier.

The Son of Neptune
Otrera was one of the people Gaea revived from the Underworld using the Doors of Death. Otrera began persuading some of the Amazons to turn over to her side later planning to challenge the current leader of the Amazons, queen Hylla, to a fight to the death over the control of all the Amazons. Planning on winning the fight against Hylla, Otrera would help Gaea and the giants to destroy Camp Jupiter by bringing the Amazons as reinforcements. It was around this time that Percy Jackson, Frank Zhang, and Hazel Levesque find the base of the Amazons in Seattle. Otrera wants to kill them right away, but Hylla says that it wasn't the Amazon way and has Frank and Percy put in cells. However, Otrera manages to have her followers guard the two demigods. Hylla comes up with a plan to help them escape and at the same time to make Otrera's guards and therefore Otrera look bad. After they escape, Otrera challenges Hylla for the role of queen. Hylla manages to defeat Otrera in two consecutive duels in a row before Thanatos was freed from his chains and manages to keep Otrera from crossing into the land of the living again.

Trivia

 * Penthesilea and Hippolyta, other Amazon queens, were daughters of Otrera by her father and consort, Ares.
 * In the myths, Otrera is said to be a daughter of Eurus, the East Wind God, but, in the series, she is a daughter of Ares.