Marduk Kurios is an immensely powerful demon, as would befit the ruler of Hell. His powers prove to be much greater within his own realm of Hell, than in other realms. Under his reign Hell found a new hierarchy, in light of the death of the Ancient Gods. Forging alliances with other powerful demons such as Mephisto, Satannish, Pluto, Thog.... Satan was able to collect a group of lieutenants and formed the Hell-Lords. Amongst many other factions.
Marduk Kurios however is quite the deceptive entity, even for a demon. There are countless numbers of beings he has impersonated and there has been several other demons claiming they are Satan for example Chthon, Mephisto, Lucifer, Satannish, Beelzeboul and Azazel. So it is not clear exactly what is the truth, but demon being notorious liar, ensure that the true origins of Marduk Kurios may never be known. But there are pieces to be put together.
Marduk came to rule a realm of Hell by defeating other demons and assuming control. This creature had existed long before human lips formed the word ''Satan'', the Sumerians had a name for him. A people so ancient they could trace the lineage of their kings before the great (biblical) flood. So ancient that they recorded the times when feuds in Hell were actually fought on Earth. The Sumerians saw the creature win his tract of Hell in battle, and in righteous fear or the awful things it did on that day, they fell into worship of the beast. And they recorded his name well.
Approximately 200 years ago, the Somnambulist raised Satan in Jericho, Nevada. Satan slew 400 of the 500 residents and rote a book with the bodies. Eventually Satan was defeated by a supreme sorceress, banished back to Hell, and his cultists slain. There now stands a monastery on the site of that horrific event. Also the location of Satans greatests literary works.
At one time the hell lords had sought to create children via a human woman form. Intending that this son would serve as a living battery drawing in the black energy of mankind, storing it up as pure evil. This is what led all demons to want to father heirs as it were.
Mayor Story Arcs
Birth of Hellstrom
Marduk Kurios Fathered two children with a innocent woman he seduced and soon after married. The first child was a male named Daimon (Hellstorm) and the second, a female named Satana. Their father trained them constantly in the black arts. Especially Satana, who showed more interest in the teachings. Satana earned her father's affection through the mutilation of birds and other such obscenities.
After some time Marduk asked his son to join him at his side in Hell and promised such great power, but also told him to think about it. Emerging from this, Daimon realized that his father stood against everything he cared for and resolved that he must destroy his father. Daimon did not destroy his father but he did defeat him. Weakening him... for a time. However his powers are still almost unmeasurable.
Marduk can be seen as one of the demons at The Infinite Embassy, more precisely he was at the Devil's Advocacy, inside the Embassy, arguing with the other demons who should be the true Satan.