Giving Yovana freedom and letting her use Atlan's body in exchange for the stone? Or stopping her and risking the lives of his friends? That was the question before him.
He knew what Lilith's answer was going to be. She was going to say no. As for Lancaster, he was going to support whatever he said since there were no stakes for him personally in this. It was for him to decide what to do.
"Okay. I've decided." After taking a brief moment to think about it, Atlas declared.
He had arrived at a conclusion, and that conclusion was to stop Yovana. She wasn't something he could trust. If they let her leave, who knew how strong she could become? And surely was going to find it suspicious if they asked for the Key Fragment, which could make her realize that they had ulterior motives.
There were too many uncertain factors in letting her leave. Those factors made Atlas come to a decision.