Simion Pentasian
Simion Pentasian was the Master of the Administratum during the Horus Heresy. A dour and humorless man, Pentasian was nonetheless a faithful servant of the Imperium who managed to hold together the vast Administratum.
During the Heresy, Pentasian fought against the attempts of Vethorel to try and promote the Mechanicum to Adeptus status, which would give them a formal seat on the Council of Terra.[1] He reappeared during a Council meeting in the early stages of the Siege of Terra. By this time he had taken up drinking and despite having much of his powers stripped by Rogal Dorn's martial law still dutifully carried out his tasks around the clock.[2]
Pentasian survived the Heresy and became one of the members of the Grand Council of Reconstruction to rule the Imperium in the turbulent period of the Scouring. He was lobbied by Master of the Chosen of Malcador, Khalid Hassan, to assert the power of the High Lords of Terra as a counterbalance of the Primarchs, which he saw as dangerous given the events of the Heresy. He also demanded a seat on the Council, and these demands were dismissed by Pentasian as ludicrous. Pentasian went on to support Roboute Guilliman's plan to retake Luna, which may have just been a cynical ploy to reassert the Administratum's power by reacquiring its logistical and administrative network.[3a]
Pentasian came to view the Chosen as obsolete, and expressed his desire to seize their assets for himself during a meeting with Hassan. However this Hassan instead revealed itself as a Callidus Assassin, as he had become the new Grand Master of Assassins. Faced with death or compliance, Pentasian agreed to back down and ensured his cooperation as well as agreeing to give Hassan a seat on the Council.[3b][3c]
