Forgotten Memories: The Legend Begins!

When someone who was once a supreme existence suddenly forgets about everything about himself, what will happen?

Especially when he was summoned by a low level mage to become a slave will he do it?

Even with his forgotten memories will it will be enough to stop what was destined to be his?

Note: The title is not really the real title and so is the synopsis. But their some connection between them. I just did this to make it more thrilling, cause the title will spoil everything.