Skullgirl

The Skullgirl is a powerful female being that is the result of an "impure" woman making a wish using the Skull Heart, an object which later merges with the user. Skullgirls are intended to be mindless servants of the Trinity and are tasked with destroying the world, but those with a strong will such as Marie can resist the Skull Heart's influence. Even those who can resist the Skull Heart however experience considerable changes in their personality, becoming more cold and ruthless over time. Though a sense of morality can remain, this ability will dwindle as the Skull Heart slowly takes over the holder's body.

Parasites also become corrupted if their host becomes a Skullgirl. They lose their sense of individuality, though whether or not this means they remain as a separate entity or become one with the Skullgirl or Skull Heart remains unknown.

In When the Cold Breeze Blows Away, it will be happened in during World War III that they are happened in during USRAC War.

Sometimes,they are allied or against Grand Alliance,Coalition of the Red Star and Global Liberation Union in their choices like neutral enemy or friendly neutral,which they would be dependent themselves to join or against Grand Alliance,Coalition of the Red Star,Global Liberation Union,Beleninsk Pact and New Central Powers

Therefore,some Skullgirls are archenemies like Nancy Renoir and Selene Contiello but some Skullgirls are heroes or faction members or former enemies like Filia Medici - female hero who was one of potential Skullgirls,or Sara Zodelin - member of Black Egrets who Inkwell Isle's Skullgirl.

Good Skullgirls or allied Skullgirls would be defended by New Central Powers in during USRAC War and except for enemy Skullgirls.