From Lexicanum

The Regent of Terra was a position held by one of the highest ranking members of the Imperium of Man during the latter years of the Great Crusade.

Overview

The Regent was one of the highest titles present among the Emperor's Imperium. They were one of the few positions that warranted the placement of members of the Adeptus Custodes who served as his bodyguards.

History

The only known Regent of Terra was Malcador who met with Death Guard Adeptus Astartes Nathaniel Garro and former Sons of Horus Marine Captain Iacton Qruze on Luna in order to discuss the formation of new branches to the Imperium to combat the forces of Chaos.

Source

• The Flight of the Eisenstein by James Swallow