In Greek and Roman mythology, a palladium or palladion was an image of great antiquity on which the safety of a city was said to depend. "Palladium" especially signified the wooden statue (xoanon) of Pallas Athena that Odysseus and Diomedes stole from the citadel of Troy and which was later taken to the future site of Rome by Aeneas. The Roman story is related in Virgil's Aeneid and other works.
In English, since circa 1600, the word "palladium" has meant anything believed to provide protection or safety — a safeguard.
Palladion serves as the initial Persona of Aigis. Her skill set consists of physical attacks and status enhancements. Once players reach a specific point in the story, Palladion will become Pallas Athena. By comparing Palladion's cold, mechanical design to Aigis' initial, mechanically programmed personality, Palladion represents Aigis as an android. When Aigis recognizes and accepts her emotions and humanity, Palladion becomes Athena herself rather than a model or representation of her.
Apart from her appearance as Aigis' Instant Kill, Palladion also appears as a palette swap for Ariadne when Labrys is using her Aigis palette. This gives her the distinction of being the only Persona in the game who appears as both a usable Persona and as an alternate palette.