English borrowed aegis from Latin, but the word ultimately comes from the Greek noun aigís, meaning “goatskin.” In ancient Greek mythology, an aegis was something that offered physical protection.

Aegis is the original spelling, and it is Aegis in the Japanese version. But they pronounce it as "Ai-gi-su." To fit this pronunciation, Aegis's name became "Aigis".

Aigis appears as an android with short, blond hair and dark blue eyes. As she is an android created to fight shadows, her body is mostly mechanical, although she retains a human-esque figure with a face (presumably to facilitate better interaction with SEES and other humans).

In the Journey, Aegis starts with Palladion, which evolves to Athena later. The MC, who is a wild card, starts with Orpheus. In the aftermath of the Journey, The Answer, Aigis becomes a wild card and her persona is replaced with Orpheus.