"Wait a moment. All five of you have True Names... how is that possible?" Zaila's Primordial Spirit asked, acting like an entity of its own.
This begs the question: just what is she?
The fact that she looked shocked means she clearly has her own reasoning, which suggests she is more than an entity formed from Zaila's soul.
If that was the case, then the question should be: What is a Primordial Spirit, and what do they stand for?
They clearly have a mind of their own and can reason independently, even exhibiting all the signs of a person who has their own free will. This means there is a lot to unpack from the concept of Primordial Spirits.
First, however, the question must be answered.
"They have True Names, which were given to them by Kent," Vexthra answered. She knew something profound was happening here, and as the most intelligent among her sisters, she ought to know.