This is the re-vised version of the Origin of Rexdian a.k.a. Masked Lion (Expect the some changes,because I wanna make it for the true Japanese version of Sailor Moon,whether is 90s or Crystal version)
-Part 1,it takes place 8 years before the Dark Kingdom invaded the Moon Kingdom-
Sir Prince Trevor of the Stars was born on a water based planet called Aquos. He was raised by his parents Roy and Lisa and they taught Trevor the way to uphold the Royal Star Lineage and was deteremind to become the next ruler of the Star Kingdom when his is older. He had a wonderful childhood,but then one day,everything will be changed. While Trevor is 6 years old and having the best time with his parents in the Royal Star Castle,but then dark clouds hover over the kingdom,but then dark monster spring up out of nowhere. The monsters started killing a lot of Royal Star residents and they evacuated to the castle,but there were too many monsters and the people are dying. Then the Shitennou (Four Kings of Heaven) appeared along with their ruler Queen Beryl. As Beryl ordered the kingdom to be destroyed. Almost of the Royal Star residence are all as the Dark Kingdom army was aiming for the Royal Star Family,Roy fought off the Shitennou and Roy defeated them all,but he was stab through the back by Beryl and he was killed easily. Then Beryl stare at Lisa and her child Trevor in Lisa's arms and the last words Beryl said to Lisa is "It's time I take what truly belongs to me,sister." (Spoiler Alert: Lisa and Beryl are sisters). Beryl stab Lisa through her heart with her dark staff while Lisa died while protecting her child. Then Beryl grabbed Trevor and took him away from Lisa's dead body and Trevor was taken away from the Star Kingdom to the Dark Kingdom.
-Part 2,this is how he got his new name and his dark powers-
Trevor has been absorbing a lot of dark power while he has been captured,but then he has finally absorb all the darkness within him and he has now pledge himself to Beryl and the Dark Kingdom. Beryl has given Trevor a new name and title- Rexdian "Son of Beryl". Rexdian has been ordered to be train by the Four Kings of Heaven in order to become the greatest warrior in all of the Dark Kingdom. Throughout Rexdian's training,he had made friends with Zoicite as they went on several missions together. Although Kunzite doesn't approve of Rexdian,he will soon grow a bond with Rexdian soon.
-Part 3,this is where the down fall of the "Son of Beryl"-
But after one mission when Rexdian was 10,he felt something from inside his head,then he passed out. After a couple of weeks,he saw an image of a Moon Kingdom,then he woke up. He gain his strength back for his next mission,but after the mission was done,he decided to visit the Moon Kingdom and he knew that image that he saw was true,but then the guard appeared and Rexdian quickly escape. He did not tell Beryl of where he went and he continued with his missions. Later on,after every mission he has completed,Rexdian has come to the Moon Kingdom time and time again,but this time Zoicite followed him,he caughted Rexdian and Rexdian told Zoicite about every location of the Moon Kingdom. Then Zoicite showed the map of Moon Kingdom to Queen Beryl and Beryl is very interested and she told everyone of the Legend of Silver Crystal and having that power will grant a person's wishes,no matter who it's user is. As soon as Beryl spoke of it,Rexdian was reassigned to scout around the Moon Kingdom and to eliminate Sailor Senshi through the galaxy. After Rexdian's first scouting mission,he stayed behind and looked around more,and then he was approach by Queen Serenity,Rexdian prepared himself to fight,but Queen Serenity didn't want to fight,Rexdian told Queen Serenity his name and he works for Beryl,Queen Serenity never heard of her name yet. But Rexdian was scared to tell Queen Serenity any more details and decides to leave the Moon Kingdom fast. Later on as the years go by Rexdian has gotten much stronger than before,and throughout the years he has killed many sailor senshi across the entire galaxy and he has commited almost genocide on the entire sailor senshi warrior race (the only senshi left are the ones on the Moon Kingdom). Rexdian is now 14,and throughout the years he had finally gained the respect of the Shitennou,that he became the youngest member in the Dark Kingdom's history to be a Shitennou (A King of Heaven). Rexdian's first mission as a Shitennou is to kill Prince Endymion of Earth for being a traitor. So Rexdian goes to Moon Kingdom and finds Prince Endymion along with another girl,that girl is Princess Serenity. Rexdian was about to attack and kill them both,but then he saw the love between both Endymion and Serenity,his conscious kicks in as he remembers all the bad things he has done and so Rexdian decided to refuse to kill them both. So Rexdian went to Queen Serenity and shockingly enough the Inner Senshi (Sailor Mercury,Mars,Jupiter and Venus) were with her as well. The Senshi prepare themselves for a fight,but Rexdian surrendered himself,not knowing to Rexdian,Kunzite is spying on Rexdian. Anyway Rexdian told Serenity and the Senshi about the assassination he was ordered to do. However the Senshi actually accepted his apology and forgive him,but Rexdian did not tell them about the Senshi genocide he was responsible for. Queen Serenity help Rexdian become his true self,but he refused to be healed by the Legendary Silver Crystal as he decided to to Kill Beryl in order to have peace within our universe. And his last words to Queen Serenity and the Senshi is,"If I don't survive from Beryl,I want all of you to forget about me,so you'll all be safe from the real truth and for that,I am sorry.". After he say that,Queen Serenity gave Rexdian half of the Silver Crystal along with it's power (you see the Legendary Silver Crystal used to be bigger until that happens )and wishes him luck. Rexdian comes back to Dark Kingdom,but Zoicite and Kunzite stops Rexdian and attempts to kill Rexdian for disaobeying orders,but Rexdian defeated them both and runs to Beryl. Rexdian finally arrives to Beryl and this is what he said to Beryl,"Beryl I know everything that has happened and I know what you were trying to do! I did not kill Prince Endymion and Princess Serenity because you are actually jealous of Serenity's beauty and I know you wanted to destroy the Moon Kingdom and I won't let you do that!". Then Beryl attack Rexdian and Beryl told Rexdian that he is a disappointment and would kill him. Both Beryl and Rexdian battle each other that will change the fate of both of them. But in the end,Beryl struck Rexdian in his heart,and he falls to the ground dead. Then Beryl sucks all of Rexdian's dark power,but it did not take away Beryl's Curse on Rexdian's body,then Beryl ordered his body be taken to a place called the "Dark Dungeon" (a dark place where they put dead bodies and their souls are trap for all eternity). And his body would be there forever,or so you would seemed.
-Part 4,this is where his road to redemption begins-
After Rexdian's death,the Moon Kingdom's destruction began (we all know how it turns out),but then while Queen Serenity used to her Silver Crystal to destroy Beryl and the Dark Kingdom,Rexdian's Silver Crystal reacted to Serenity's Crystal,thus freeing his body and soul out of the Dark Dungeon and transporting him into a Time-Space dimension,where his dead body was discovered by Sailor Pluto. Sailor Pluto was about to get rid of Rexdian's body,but then Pluto found the Silver Crystal and has decided to take care of Rexdian. She healed his wound where he was struck in his heart,but Rexdian was still dead,so Pluto advanced Rexdian's body age 5 years (Rexdian's age is 14,so his body age is 19 at the time),after Pluto advanced Rexdian's body age,it took time for his wound to heal as his body aged,but then he slowly wakes up,but the draw back,is him having amnesia and he doesn't remember anything about his past. Sailor Pluto ask Rexdian about himself,but the only part he remembers about himself is name. Since Rexdian carries the Silver Crystal,Pluto will do anything he wishes. Since Rexdian remembers being nice to everyone during his childhood life,so he wants Sailor Pluto to become friends and has ask her to train Rexdian,in which she agreed. So Sailor Pluto trained Rexdian throughout the course of 2 years throughout martial arts and using weapons. (I'll them out which martial arts they are soon) And so Rexdian wants to use his skill he learned for good,but he want to do as a masked hero but doesn't know how. Then Sailor Pluto told Rexdian about the Legend of the Moonlight Knight and how he is the subconscience of Tuxedo Mask,Pluto showed what Moonlight Knight and Tuxedo Mask looked like. And so Rexdian got himself an idea,along with Pluto's help,he made a costume based his favorite of black (for a badass) and blue (the color of hope) and his favorite animal: the lion (based on the courage he would give to other scouts later on) and the costume is made and Rexdian put on the costume along with a transformation wristband,that will help him be in disguise from the hero form and his normal form. And with the power of the silver crystal,the crystal made the Moon Halberd (cause he got the silver crystal from Queen Serenity). The Halberd was given a small cape on it as a sign for his forgiveness he will soon remember and thus the Masked Lion was born. He thank Pluto for his training and he was set off into the time Sailor Moon was around in Japan and thus his journey into Redemption begins.(also the Moon Halberd's bladed parts are made of Plutocranium,yes it's a fictional metal that is stronger than titanium)
So this is the extended and Re-vised origin of Masked Lion. I hope you enjoyed reading it.