Rachel

Rachel (라헬, Lahel/Rahel; "Rachel"), also known as Michelle Light (미쉘 라이트, "Michelle Light") was Bam's best and only friend as she was the only one to visit him in his "cave". She longs to see the stars which is one of the fabled rewards waiting at the top of the Tower, because she "fears the Night."

[Spoiler] Like Bam she is an Irregular. [/Spoiler]

(Source: Tower of God Wiki)