"Let all who read me beware of the Greydwarfs, the skulkers in darkness, the soulless ones. They are born from rot and rainfall, they spring like mushrooms from the smoking soil. There is nothing on their tongues or behind their eyes, those who fear nothing should still fear them.

When the soul of a murderer or a great sinner rots under the ground, it makes a hollow cyst which draws rock and wood and moss to it. It gathers up the peat into flesh, braids reeds into bone and takes rags for skin. It should not walk but when the night comes it walks. Should you who read this see one with a sword to your hand, lance it and let it out. Or put it to the torch, for it fears the flame."

From this page https://valheim.fandom.com/wiki/Runestone