A hulking creature made of bone and sinew.

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

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)

While investigating an ancient Dwarven passageway. It leads to stone altar and coffin containing Adlan. The altar is guarded by a bone golem. - Explorers Guide (GS-Guide-ADV3-24)