Dark Lord

The Dark Lord, or the Nameless One, Infernal Master and Lord of Hell is the supreme ruler of the realm of Hell. He made an unseen appearance as the Demonic voice in Doom (2016) that contacted with Olivia Pierce. Right under him in hierarchy there's the Order Of The Six, formed by 6 archdemons, one of them being Erebus, ruler of Dis. Some time around the Slayer's arrival on Argent D'Nur, he made a pact with the Khan Maykr; in turn for more worlds for Hell to consume, the Maykrs would receive the Essence, which combined with Wraith energy creates Argent energy. This lead to the construction of the tower of Nekravol, built by Sentinel slaves for Maykrs couldn't go to Hell, and demons couldn't go to Urdak. After the Icon of Sin awakens however, the Holy Seal of Urdak is broken, meaning the demons can go to Urdak, and not only is the pact broken, but the demons invade(and conquer) Urdak. He might be the next antagonist in the series, given how it is rumored that the current iteration of the series is going to be a trilogy.