Penthesilea is based off Greek mythology, in which she is an Amazonian queen. She is the daughter of Ares, god of war and Otrera, queen and founder of the Amazons. According to the legend, Penthesilea accidentally killed her sister Hippolyta, and as penance for her actions, she joined in the Trojan War, leading the Amazons to battle. She joined the war in its tenth and final year, and was killed by Achilles, who fell in love with her right when he killed her.
Penthesilea is the initial Persona of Mitsuru Kirijo. It carries an affinity to Ice, and appears as an iron-masked queen wielding a dagger and a rapier.
Penthesilea is shown to have similar abilities to Fuuka's Persona, Lucia, but to a much less powerful extent. After Fuuka joins SEES, she takes over as the group's tactical advisor, and Mitsuru joins the front lines.