Charles Ellicott Commentary 1 Chronicles 1:54

"chief Magdiel, chief Iram. These are the chiefs of Edom." — 1 Chronicles 1:54 (ASV)

These are the dukes (chiliarchs) of Edom. — Eleven names only are given, whereas there were twelve (or thirteen) chiliarchs of Edom (Genesis 36:15–19; see Note on 1 Chronicles 1:35–37). A name may have fallen out of the ancient text from which the chronicler derived the list.