The rest of my story is so long, I'll tell you the rest here.
The Emperor clouded my mind that day when I confronted him, and showed me the past. Veradun was a friend of mine, he taught me the ways of the Sith and we both served the Emperor. But as we grew stronger, so did our lust for control of the Empire. Veradun then told me that he and I should confront the Emperor and kill him. I was to confront the Emperor first, while Veradun was to attack the Emperor from behind. The confrontation was a deadly battle. The Emperor set several of his Sith apprentices to attack, and while I struck them down one by one, Veradun attacked and he crossed blades with the Emperor. After killing all the Sith, I joined Veradun in battle. It was a furious duel, and Veradun was overpowered by the Emperor's lightening and he was knocked out by a force push. I finally gained the upper hand but before I could finish the duel, Veradun awoke and flung his lightsaber at my face, giving me the scar I have now. Veradun then told me that the Emperor considered me a threat, and decided to draw me to the dark side in order to betary me, since I would never expect an attack from a friend. The Emperor and Veradun left me for dead, but I survived. But at a grave cost. The Emperor had wiped my memory, and I didn't know what happened during my time as a Sith.