Nathaniel Callaghan is a main character in Scattered Remains: Requiem, and Scattered Remains: Dual Destinies Volume Two. A former ex-con who has a criminal past, he joined the DoubleHelix Armed Forces to avoid prison time. It was here that he reunited with his sister, Isabella, and met Ambrosine Worden, both who would be important people in his life at DoubleHelix.

A lowly private at the beginning of Volume Two, he became promoted to Sergeant after saving Swifty from an assassnation attempt, and later became her bodyguard along with Jack.

5 years later in SR: Requiem, he remains her bodyguard even after both of them were no longer in the army, as part of a promise he made to someone.