Blodstones, also known as vampire stones, are a form of magic crystal. They grow wherever blood has been spilled, especially battlefields and the not-so-clean surgeries.
Stone magic is the easiest to control and is arguably the best of the four magics. It not only has all of the abilities of the other three, but it also lacks the cost those bring too. It may not be as powerful, but it is a preferred system to use.
Weilders can shape this magic with greater ease than any other. As it draws from the stone, the user has no energy loss, so they can therefore keep working for longer.
Abilities include creating and uncreating minor things, transformation, blasts of energy and what is known as glamours or illusions. However, there is a cost.
The stones feed on blood and are unable to keep chanelling magic without. They call for a constant supply, and because of that the standard is for any who want to use this magic to have the stone implanted or sewn to them, This enables them to use the magic at any time.
Unfortunately, the stones grow when feeding on blood.
The stone will grow and eventually break the skin, whereupon weilders are advised to have it ground down. Some don't and let the stones grow until they can no longer bear it.
The number an size of the stones does not effect how powerful the magic is. That is solely down to he induvidual.