Eponymous dead man
The Eponymous dead man is located south of the Dead Man's point marker in a rocky "shrine" looking area, which is surrounded by two Skeletal Frost Giants.
Inside the rocky shrine, there is skeletal remains of the dead man, there will be sparkles to indicate you can interact with it.
Doing this will grant you the achievement, giving the title "Seeker of the Dead".
The coordinates on the map should be (116, 1880)