The Dark Kind came to the world as conquerors. They failed. Now they are odd neighbors.
HeartKind bands are a way for Dark Kind (or any Deamonic/Monsterous kind) to show that people have nothing to fear from them.
As part of The Pact that ended the Six Stars Demon Wars, various places were given over to the Dark Kind. This is their neighborhood in the city.
If thrown into a moat or a ditch, they react with water to make an area of ground a foot wide and solid enough to walk on rise from the bottom. If eaten-well, the body of the one who ate one of them is a real mess. Used to storm moats and forge rivers, streams and ditches. Must be kept dry until used.