Blood Ivy

There once was a young woman with the most fascinating of Armaments. It was able to grow all sorts of manner of flora some of which this world has never seen before. Rainbow hued trees and spiral shaped flowers. Anything she would coose to create could be fashioned with a though and a wave of her sword. She was content to garden for her small mountainside village growing food and marvels alike. Vegetables and fruit that her people wouldn't have access to and healing herbs that would work miracles. She was always quick with a smile and a wave for any visitors who wanted to see, and always easy to deposit those outside the village who didn't want to be nice. Giant walking trees have a habit of turning off those who want to take from them.
At least it did most of them. But The King and his Crusade would not be turned away so easily. He decreed her Armament as being too dangerous to be left in anyone's hands. And not even her awesome power could deter his armies and himself. At the last second she made a decree of her own. That no one would have her sword anymore. They cornered her in a cave and she stabbed herself with her sword causing an eruption of flora too spread across the side of the mountain and beyond. To the point where a long red ivy can now be found across the realm.
Despite everything the ivy doesn't harm. It heals. It can eat away sickness and rot, infection, frostbite and more. All by mashing it into a poqder or paste and applying it to the area or ingested. Remarkably the vine also seems to grow and flourish where it is needed most. Travelers find it right when one is wounded, or a mother can't afford to pay a doctor and finds a sprig around her window. It's not always there, but it can be.
I think in the end the King's crusade had to happen, but this moment turned a lot of people off of his mission, and I think in some ways it did change him a bit as well. He chose mercy a few more times than anyone expected, but his hardness would never fade away.