Umbra: DC Universe story (Supergirl x male reader)

Before the Justice League, there was a Warrior in the days of old who is now just a hoax or a myth to many people today. The warrior was named Umbra and he was the most powerful warrior in history.

It is said he has faced many gods and goddesses, and defeated them all with only his sword, the Akinagota, a special Katana forged by the Ancient Ones of the Multiverse, the ones that were responsible for creating the group of warriors named The Tenno, these warriors saught to keep the entire Multiverse stable and safe.

With his people in danger and at war with the enemy who saught to harm and take their freedom away, Umbra set out to find a way to bring piece to both his people and the enemy, so he made a deal with the Ancient Ones that he would pledge his undying loyalty if they help him bring piece and justice to his people and his enemies so that all could join as one... This is where he got his main weapon: the Akinagota and his long life span due to his pact with the Ancient Ones.

It all seems like a fairy tale in children's books, people don't believe the history behind Umbra and the Ancient Ones...

Until they are proven wrong by Umbra's sudden return for the first time in over 500+ years, saving a group of Heroes from a common enemy of his he thought was defeated long ago...