Who is Peach (aka Winged Defender; Athene; Thor; Prometheus) from High Wizardry and what is their importance?

Peach is a Macchu Picchu. She presents herself as a well spoken bird with a great deal of attitude and sports a three foot tail of scarlet feathers. Over the course of the novel, Peach is revealed to be one of the Powers in a final confrontation with the Lone Power.