Seleucus I

Maceonian King of Asia Seleucus (c. 358-281 B.C.), son of Antiochus (one of Philip's generals), fought in the Companion cavalry and later became commander of the crack heavy infantry formation, the Hypaspistae. He took Perdiccas' side immediately after Alexander's death, but was later instrumental in his murder following the failure of the Egyptian campaign. Antipater appointed him governor of Babylon in 321.

Link: http://www.historyofmacedonia.org/AncientMacedonia/SeleucusI.html