The Villainess Needs A Tyrant
In her past life she was tricked by her uncle and cousin into giving up her succession right and agreed to marry the emperor and spy on him. The emperor fell in love with her even though he knew she was a spy, and he hoped she wouldn't betray him in the end. One day she overheard her uncle's plan to assassinate the emperor but she was poisonned by her cousin before she could do anything. She went back in time and decided to go to the emperor and get revenge on her family. Turns out the emperor went back in time too, and he still loves her. They've confessed everything to each other. The emperor's brother is still alive and her family is plotting to put him on the throne. One of the emperor's men has betrayed him and has injured another one of his men (that man has an ability to "see" with his eyes, that might be compromised because of the injury). That traitor's intention might be to save her since he is in love with her. Her male cousin owns a ring similare to hers and remembers his past life too. They were very close when they were young (she thought he was a girl) and he vowed to always protect her. One day his mother introduced him to the emperor's brother and he was ordered to put him on the throne. He agreed but soon after, Marybelle married the emperor, making her a target for assassination. He pleaded the emperor's brother to spear her life and he promised. But eventually Marybelle was killed by her cousin and he realized how naïve he'd been. He killed himself but went back in time because of the ring. He decided to protect Marybelle at all cost and to take revenge by killing all those who took part in her death, starting with his mother.
A Star Reborn: The Queen's Return