Theopompus' reign is associated with the first Spartan conquest of Messenia and with the creation of the ephorate, an important civil magistracy present in several Greek states of Dorian origin (although this creation is most often attributed to the Spartan legislator Lycurgus).
Bouchard, Elsa. "Kingship of Theopompus at Sparta". The Literary Encyclopedia. First published 01 March 2010
[http://www.litencyc.com/php/stopics.php?rec=true&UID=11143, accessed 01 October 2014.]