He was originally in command of a company known as the 'Dancers' during the campaign for the compliance of Nurth, a desert planet that had (as Imperial forces would later learn) been touched by a Chaos God, most likely Khorne, referred to as a "Primordial Annihilator".
Soneka's 'Dancers' were all but routed by a surprise Nurthene attack during the campaign against the Nurthene city Tel Utan. It was later revealed that Soneka's company was intentionally used as a diversion by the Alpha Legion in order to draw the enemy out of their fortified city, thus allowing Alpha Legion Astartes to infiltrate and sack it. A disillusioned Soneka was retired to a town known as Visages with what remained of his Dancer company, and was shortly attacked by Nurthene raiders and eliminated entirely, barring Soneka, Lon and Shah, two of Soneka's subordinate Bashaw's, and a handful of troopers.
His reputation for loyalty and close friendship with Jokers company Hetman Hurtado Bronzi eventually brought him into the service of the Alpha Legion, serving as a would-be spy for the Legion within the Imperial Army. He later escorted John Grammaticus to the captivity of the Legion, and finally to the surface of 42 Hydra Tertius to meet with the Cabal.