In Stranger Things, Eleven’s sister with the number Eight tattoo is Kali Prasad.
Kali, also known as Eight, appears in the season 2 episode “The Lost Sister.” Like Eleven, she was taken to Hawkins National Laboratory as a child and became part of Dr. Martin Brenner’s experiments. Kali’s ability is to create convincing illusions in other people’s minds, whereas Eleven’s best-known abilities involve telekinesis and remote viewing.
Kali escaped the laboratory before the main events of the series and later formed a small group in Chicago. Her story gives Eleven a wider view of the children affected by Brenner’s program. The characters are called “sisters” because they shared the laboratory’s numbered test-subject system, not because the series establishes that they have the same biological parents.
Kali is played by Linnea Berthelsen. The episode also introduces the idea that trauma and anger can influence how the numbered subjects use their powers.