The Soul-Devouring Vine is quite special; it can devour the spiritual power of humans, beasts, and plants to strengthen itself.
Because it was so defiant of the natural order, it was once classified as one of the Forbidden Beasts.
Later, people discovered that the Soul-Devouring Vine wasn't as harmful as imagined, because this plant Spirit Beast wouldn't actively kill for spiritual power; it just needed to get its fix once a month by drawing some spiritual power.
It even became very tame after contracting with a human Beastmaster. Most crucially, it cultivates spiritual power at a rapid speed through meditation.
So, people later developed a beast taming method for it, where Beastmasters with strong spiritual power allow it to absorb some once a month.
