Lady Saisho is the oldest tree in the world. She didn't originally have a consciousness, but when she started to understand the world around her, she began to understand her role.
Since before she could even remember, her body produced spirits. These served as natural cleansers to the magic in the air. The spirits were so numerous, but the original spirits served to sweep away the miasma. Mana and miasma were two sides of the same coin.
They were fundamental forces that governed the world of magic, and they weren't the only ones. There was something even more vast called divinity. However, the stronger the forces of magic, the harder they become to understand. If one performs experiments, one can expect that a blow back would be worse with a stronger force.
