The Shunned Son

Lucifer was one of the most beautiful angels the Heavens had ever seen, he was also a strong warrior. He fell from grace and was banished to Hell, where he became ruler over the wicked souls. Even though he was in Hell, he could enter the human world. He met a young lady named Ririka Ucha, a member of the Ucha excorist clan. He told her his name was Alabaster Cross, they would get married and have three sons. The eldest was Alistair Cross, the second was Leonard Cross, and the last of the sons was Damian Cross.

The sons indeed cherished both their parents, their mother taught them how to live and be human in addition to their lessons in excorism sand their father taught them how to use their demonic powers. Alistair's power was an dark oil-like substance that could take the form of a black flame which he took to calling Tar. Leonard was a brilliant fighter and excellent swordsman, he could make a weapon out of anything. He can transfer his demonic energy into any object and form it into a weapon, he was often referred to as the Wielder.

However, Damian had a different power. He could do something that no one could do. Not an angel, demon, his brothers nor even his father could do. Damian could summon and control the darklingss from Tartarus, the darkest part of Hell. No one else could/can access it except him.
One day while the brothers were training, they met a young woman named Kagi Uchiha. She was the most beautiful woman the boys had seen in their eternal lives. While Damian didn't have any particular interest in her, his brothers wanted her for themselves. For months on end they would attempt to impress her, upstaging each other at every move. One night, Leonard took Kagi on a date and didn't inform Damian or Alistair. Later that night, Alistair would confront his brother after finding out about the date, he and Leonard got into a physical fight because of it.

Damian came into that area at the most gruesome of moments, when Leonard rammed his sword directly through Alistair's heart. Alistair saw Damian in the shadows and his soul attached to his brother's, giving him absolute mastery and control over Tar.

Seeing Alistair die in such a way by his own brother's hands was too much for Damian, he unleashed a Darkling upon Leonard. This Darklings was stronger than the normal ones, it tore through his brother. Damian approached his brother's body, placing a hand on it. Damian absorbed Leonard's soul and fused it with his own, giving him Leonard's power as well. He would return to Hell with his brother's dead bodies, only to have his father scold him and send him away. Banishing him from his home, yet Damian found a new home. In Tartarus with all the vicious, horrific beasts he would come to control and come to love.

Damian trained with many warriors throughout his lifespan, he fought as a samurai. Damian met a man named Raumi Kikiro, he was an excellent samurai and a captain of the Serpents of Kaiyami (the fiercest warriors). Even though Damian was well into his three hundred years of age, he still looked to be in his early Twenties and Raumi offered to train Damian.
Raumi taught Damian several fighting styles, including Initaki which was his clan's secret fighting style. It consisted of using you rentire body as both a defensive and offensive weapon, Damian was used to this so he accepted. Damian excelled in his training, Raumi was proud of him. A war fell upon Raumi's village, Damian enlisted in the Serpents of Kaiyami so he would be of help to Raumi.

Damian showed the Serpents how ruthless he was, some feared him even though he was helping them. The Serpents slaughtered the invaders, leaving them left with one last mission. Damian voted they storm the village that sent the invaders and show them the true meaning of war, Raumi didn't approve of it yet he knew Damian ahd so much truth. The Serpents marched for days until they found the village buried in snow, they attacked violently.

The village ended up killing some of the Serpents, this angered Damian more and more with every death. He stabbed his sword into the ground, causing a giant rip to appear, a battalion of Darklings flood from crack in the ground and begin to devour the remaining villagers. The Serpents were untouched by the Darklings, Raumi looked at Damian with shock.

After Damian sent the Darklings back to Tartarus, Raumi approached him and said, "If you had this much power, why did you follow us? We are humans, our deaths shouldn't matter to someone so powerful." Damian was silent, he turned his back to Raumi. "Because you all were my brethern. The only brothers I've had in centuries." Damian said then Amaterasu would consume his body and he would go back to Tartarus.

Pwr Lvl.- Kage

Leave it to a woman to get two brothers to kill each other. *Shakes head* Question, what even happened to the Kagi chick?

It's a good story, especially since I expected a more "I'm the son of Lucifer, all will bow to down to me, kill kill die die!" The only few discrepancies that will arise due to plot on Mylania is the fact that Tartarus is the final abyss, a prison for even God's. Meaning if you went there or lived there, you should have no way of getting out. Even Zeus, God, Aries, Posiedon, etc. would not be able to escape from Tartarus. The only exception that I can see with this is that you weren't cast there, so you aren't condemned to Tartarus.

Second, you wouldn't be the sole person able to go to and manipulate Tartarus.

Third, we'll need to discuss Lucifer on here seeing as Hell/the Spirit Realm is an actual place. Meaning Lucifer will need to be an actual character. This will need to be discussed with all of the admin.

As far as it goes with her, she just lived the rest of her life out and died.

And you would be correct in that exception. Only if you are sentenced there, are you unable to escape. Damian was conceived and born on two nights where the planets and stars were in a specific conjunction which allows him his ability to travel through and manipulate Tartarus.

Now, when it comes to your second point, of that I am quite sure, however the only other people that would actually be able to are those of Celestial heritage or high mystic level oppose to someone that's just able to walk through dimensions.