Callista is the daughter of Elaine and Max who receives the second skin
in vivo. It misinterprets her infancy as a condition requiring healing. As
a result, she matures incredibly fast, becoming conscious in the womb
and teleporting herself out of her mother’s body at one point.

She rescues Max in Book Three by helping him fight Aggregar (Lord of
the Assemblers), and goes on to play a pivotal role in Book Four at
which point, chronologically just over one year old, she already looks
and acts like a 20-year-old.