Penthesileia

Penthesilea (Greek: Πενθεσίλεια) or Penthesileia was an Amazonian queen in Greek mythology, the daughter of Ares and Otrera and the sister of Hippolyta, Antiope and Melanippe. Quintus Smyrnaeus explains more fully than pseudo-Apollodorus how Penthesilea came to be at Troy: Penthesilea had killed Hippolyta with a spear when they were hunting deer; this accident caused Penthesilea so much grief that she wished only to die, but, as a warrior and an Amazon, she had to do so honorably and in battle. She therefore was easily convinced to join in the Trojan War, fighting on the side of Troy's defenders.

Penthesilea arrives in Troy at the start of Posthomerica, the night before the fighting is due to recommence following Hector's death and funeral. She came to Troy to prove to others that her people, the Amazons, are great warriors and can share the hardships of war and to appease the gods for accidentally killing her sister Hippolyta while hunting. She arrived with twelve companions and promised the Trojans that she would kill Achilles. According to Quintus, Penthesilea was such an effective warrior because, unlike most Amazons who were missing a single breast, Penthesilea had both breasts cut off. On her first and only day of fighting, Penthesilea kills many men and clashes with Telamonian Ajax, although there is no clear victor, before she comes face to face with Achilles, who had been summoned by Telamonian Ajax. Prior to Achilles' entrance, Penthesilea had tried to fight Telamonian Ajax but he had merely laughed off her attempts, thinking her an unfit opponent. With only one blow Achilles pierces her breastplate then proceeds to impale both her and her horse. At first he mocks her corpse until he removes her helmet and feels strong remorse.

Proclus, who summarized the lost epic poem, the Aethiopis of Arctinos of Miletus, of which only five lines survive in a quotation, gave the events of Penthesilea's life. The story of Penthesilea segues so smoothly from the Iliad in the Epic Cycle that one manuscript tradition of the Iliad ends

...
Wikipedia