You were immortal but you had the ability to make anyone that stayed close to you immortal as well. A selfish and greedy king found out about your power and chained you above his throne, so he would live forever with your ability. After 10 years of being chained, you hear yelling a fighting. Then you faintly see the king getting pulled away from you and killed. The people let you down then you see a handsome man, walking over to you and kneeling beside you

“so you are the immortal being”