Background
Rellkir has not had an easy life. Starting off as the son of two slaves on Tattooine, he struggled everyday until his daughter was born. Cheyria. With her precious life now in his hands, Rellkir knew he had to get them out of this eternal servitude. One day, his masters having taken him and his daughter on one of their voyages off world, he saw his opportunity, attempting to flee onto another spaceship as it departed while desperately dragging his daughter behind him. With all the strength his lungs could muster, he screamed "JUMP!" to his daughter. Miraculously, they managed to make it on board the vessel just as it pulled away from the dock. But not alone. Rellkir turned to see one of his master's henchman was hanging on by his daughter's leg, pulling her down and off the ship. At the worse moment his grip loosened as he watched Cheyria's face shrink into nothingness as her and the guard fell back onto the dock.
Now left in an impossible situation, go back for his daughter (likely unsuccessfully) or press on and find some allies to help him, Rellkir went with the latter. Joining the army of the republic, serving wherever across the galaxy they deployed him. During these years of his life he saw the atrocity of slavery in all it's grotesque forms. Destroying this abominable institution became his primary goal, one that would - by extension - free his daughter. The Empire crushing the Republic was just fortunate timing for him to flee to the Outer Rim and use the skills he gained as a soldier to work as a gun for hire.
Motivation
Cause - Emancipation