Luke

History
Luke or better known by his title Darth Syndos, was a mandalorian human male trained as a Jedi for decades before deserting the Order to seek out another purpose.

Childhood and Slavery
Syndos was born to the head of a mandalorian clan, his mother died giving birth to him. This wasn't the exact reason his father mistreated him, it was more to do with the traditions of the mandalorians, this didn't mean Syndos grew to hate them. But as he grew older he saw the true reasons his father did it, his father was weak, and cowardly only wanting to hold on to his power, and he saw his son as a threat not a successor. It hurt somewhat, but Syndos learned something valuable from all of that in retrospect down the line. Sometimes you must forge your own path, others may help you along the way, but you must traverse your own path, not always follow someone else.

That lessons wasn't learned right away, for when Syndos turned young he was sold into slavery. He was a slave for four years, four long agonizing years, as his hutt master wanted to break the stubborn pride of a mandalorian, and have him be the perfect little toy as a weapon. But Syndos would not yield, and as his force abilities manifested, so too did the anger, but it was cold, and though not as controlled as it is now.

But then for a brief time he knew hope, as he was rescued from the hutts by the Jedi. When taken into the Jedi Order, at a young age of seven years old. They wanted to help heal the young boys wounds, and temper the darkness. And for a long time they succeeded, he became friends with Gavar Skywalker. They fought together, and played together. He was the closest thing Syndos considered to a brother.

Deserting the Order
As years went by, and the corruption just kept coming back, and the hutts kept ruling. And countless people were still enslaved, Syndos began to question the jedi, and the republic. Why were they so incompetent, couldn't there be more done? But ultimately he realized the only way to change anything for good, was through power. So then with a heavy heart he left the jedi order, and went exploring into the unknown regions.

There he came across Palpatine's old records, and then he found others drawn to the dark just like him. So the rallied them together, and taught them jedi ways, while learning the dark side of the force. From old records of Palpatine's he had hidden around the unknown regions. In this way he acheived a grey alignment of sorts. But it wasn't enough, Palpatine's knowledge while vast, and detailed lacked an edge.

Mission to Dagonbah
Seeking out the Force Nexus located on the swamp planet, Syndos glimpsed the same vision as Gavar who had also been drawn to the Dark Side Cave.

The two conversed before being ambushed by Jedi Sentinels and Sith Assassins who had tracked them to Dagobah and used the meeting to attempt to kill the other force user. While Gavar dispatched the assassins, Syndos easily drew on the dark side and force choked the Sentinels and fled the cave.

Battle of Ossus
Syndos alongside Requiem attacked the Jedi High Council during their meeting, using rubble caused by their entry to kill several Jedi Masters and then duel Gavar personally.