It’s theorized by Darius that Maeve may have been born to be Tam’ra’s first Priest. While he has no definitive proof of this, he reasons that Maeve displays several attributes that Priests do:
He shares his Spirit’s love of their domain
He has a deep spiritual connection to his Spirit’s domain in that the forest favored him.
Maeve, over time, developed the ability to see magic (though this ability can also be attributed to him spending such a great amount of time around Guardian Spirits and Priests during his time running the Council.)
He is deeply devoted to his Spirit.
He is immune to The Healing Plague (Pestis Paradoxicuum) which is commonly contracted by humans who come in contact with or live near a Spirit’s domain.
And also while having no definitive proof, Darius argues that Tam’ra’s lack of knowledge in regards to how being a Guardian Spirit works is because she was once human and retained her human memories instead of being reborn with a clean slate, though seeing as Balthazaar itself has shown sentience, its possible that the forest chose to let her keep her memories upon her death and subsequent rebirth.