The Challenges of Original Fiction

I've been wanting to write my own book and publish it, either hoping I can get it published by a sponsor, or self-publishing it with Amazon. But even with all the muse and Ideas I have, this is amazingly challenging, especially because it's original fiction. With fan fictions, it's easier to come up with ideas (for me at least) because other than OCs, fans know what things will and won't work on most characters. But when you're writing original fiction, it's all on you, you don't have anything as a base to start. Writing is my passion, I have a BA in English and minored in creative writing. But thinking up my own work without any sort of base or prompt? It's much harder that I realized. If you'd like to know more about my trilogy, here's some info

The titles of the books, in order, are Lords of Sin, Fall of Heaven, and Divine Retribution.

If it wasn't obvious, the books have a religious theme to them, mainly Armageddon, the final battle between good and evil. There are seven high ranking demons, one for each of the Seven Deadly Sins called the Lords of Sin.

Lucifer, who is obviously the leader of the Lords of Sin, represents the sin of pride. His title is Paradise of Loss. The other six members have titles as well and are based off demons of different sorts. Their titles in this order, Envy, Wrath, Sloth, Greed, Gluttony, and Lust are Abyss of Despair, Hellfire of Chaos, Roar of Awakening, Schemer of Gold, Duelist of Finality, and Goddess of Darkness. In the same order, the demons they are based off are the Leviathan, Satan, Belphegor, Mammon, Beelzebub, and Succubus. And believe it or not, Lucifer and Satan are not the same person, took a lot of research looking for a replacement for Satan before I found out Satan is not Lucifer.

To make a long story short, here are the basics for each book

Lords of Sin
Lucifer and the Lords of Sin invade purgatory and force its residents into their Damned Army. They plot in the shadows in order to overthrow God, kill Jesus, and destroy the world and remake it in Lucifer's image.

Fall of Heaven
The Lords of Sin are victorious in their war campaign against God, Jesus, and the Holy Knights. Heaven is destroyed and remade into a place where people can indulge themselves in the sins of daily life with no consequences. With Jesus dead, many of the Holy Knights begin to lose hope, but their hope is restored by the bravery of mortals who are rebelling against Lucifer's rule, and they join the fight once more.

Divine Retribution
The Lords of Sin begin suspecting each other of being traitors, and while the Beelzebub is a traitor, they don't find out right away. The Beelzebub is impressed by the courage displayed by mere mortals fighting for what's right. He abandons the Lords, nearly getting himself killed in the process, and with his knowledge of the Lords' weaknesses and fighting styles, he is able to help the Holy Knights defeat the other Lords for good. However, Lucifer forcibly fuses himself, the Beelzebub, and the other five Lords into a creature based off the First Beast of Revelation. Despite the creature's strength, the Beelzebub is able to weaken the beast from the inside and is able to break free and give the Holy Knights the opening to defeat the beast, sealing the remaining Lords away forever. The Beelzebub is forgiven for his crimes and becomes an honorary Holy Knight.