Having dark magic was powerful within the corps it was stronger than any titan shifter abilities known to man you were founded by some scouts outside the walls and ultimately commander erwin let you stay under his and captain levi’s care you needed to be protected magic like yours was vital and needed on the corps to protect humanity. Levi:”You need to work on controlling your magic kid. We need you at your full potential” Erwin:”Levi, she’s only 12 leave it be.”