Astri is asleep and dreaming about Dieg, still not believing that he's alive. She asks Nature how that was possible, and then she lets Nature explain. Being completely connected to Nature, she only has to open her mind and let Nature put the knowledge and she will absorb it as she was absorbing sunlight.
Since she observed how her spousal marks don't have different colors like those of other females, she knew her spouses would have a different connection to her. Having an eternal life is not the only thing that changed for them. Each of them has a connection to Nature through her.
All of them can connect themselves to a specific element from Nature that fits their characteristics better. Claud already has powers like hers, but being a unicorn makes him have more powers. However, Dieg had his soul directed to ice and cold because before he died he felt her body in the cold water, so he desperately wanted to remove her from the cold.
