Lord of Rot and Decay.

Its bones are carved with runes that glow cobalt blue. Something about the skeleton transfixes you. - Gate of Brizoor Waal (RPA-ADVF)

Native to Hoshek, Plane of Life.

When traveling to Hoshek, Plane of Life, the Rune Bones are called to a Troshag;

In the midst of all this life, you spot a dead zone. A ring of wilt and rot, encircling a humanoid skeleton resting on a large stone plinth. Its bones are carved with runes that glow cobalt blue. Something about the skeleton transfixes you. - Gate of Brizoor Waal (RPA-ADVF)