Played by Charlize Theron, Clea stepped into the Marvel universe in Doctor Strange in the Multiverse of Madness. She appeared in the post-credit scene.
She's the niece of Dormammu
Hailing from the Dark Dimension, Clea is a sorcerer. She is the daughter of Prince Orini and Umar, the sister of Dark Dimension's ruler, Dormammu.
How is Clea related to Doctor Strange?
While Clea's arc is unknown in the films, she is intricately associated with Strange in the comics—from helping him in a battle once to becoming his disciple.
She might be Strange's next love interest
Another factor that we know from the comics is that Clea is Strange's significant romantic interest. In fact, the two sorcerers are married.
What can we expect next?
In Doctor Strange 2, she takes Strange into the Dark Dimension. So, we can expect follow-up Doctor Strange movies to focus on their fight with Dormammu.