As Megames1 suggested, I'm making a champ for the the Black Knights.
Black Knights, those not only known for their black blades, but also for their blackened hearts. Known for terrorizing even in the Noxus so long ago, their stories begin similarly: A traumatic experience when they were young, being lalienated by their own, or even being betrayed. They all end with cold, swift vengence. Though it has been so long since the Black Knights have appeared, some of the elderly do remember the fear in their hearts when they slept at night, knowing that one day, the blade of Black justice will rend them.
A young demacian soldier, Lykrast was know has a good soldier, but too young to be promuted for now. Though he was quite respected, the few raids he did left him with huge wounds. His courage was still very high, despite him normally not being able to fight. But one day his captain asked him how did he survived so long, Lykrast didn't want to answer. He was then interrogated, but he still don't want to answer. But he had the bad idea to put off his armor, revealing a strange symbol.
This symbol was the one of a pact with a demon, that granted him immortality, but fragility and no soul. He was sentenced to death and sent off to the Royal Dungeon. He stayed for about one week, waiting for an useless execution, as he know he can't die. At the 7th night, he begin trying to hopelessy escape, punching the walls. His hands were completly covered in blood, with no hope left, but he continued. And finally, he broke the wall, after 2 days of punching without stopping. He escaped and then nobody heard of him for several years.
He then returned to Demacia, without apparent reason, with a dark armor and a dark sword, with blood covered in most of the blade. He walked strangely without being seen in the Royal Dungeon. He killed the guard and take his place. Approaching a betrayed boy's cell, Lykrast revealed himself as one who has also been in some way betrayed by society. He offered the boy an oppurtunity to obtain his revenge and serve a righteous group. Reluctantly, the boy joined, and escaped his prison that same day. Lykrast also vanished, and the body of the old guard was found shortly after.
NOTE : date is written Day/Month/Year