Like Weapons, they have a tier system as well, with Greater Runestones providing a larger effect than it's regular and Lesser counterparts. You'll be able to find Runestones by defeating Enemies, in chests, or by asking a blacksmith to craft one if you have the correct diagram unlocked. There https://touhou-danmaku-kagura-pha86172.onesmablog.com/os-thewitcher3-diaries-77709874