unfathomable darkness深不见底的黑暗
Unfathomable Depths高深莫测
Something Unfathomable吧不可思议
enigmatical unfathomable莫测高深
Unfathomable Theories深奥理论
unfathomable deep深奥莫测地
Unfathomable sea深不可测的海
Unfathomable Power深不可测力量
unfathomable theme思想主题
ADJ（形容词） If you describe something as unfathomable, you mean that it cannot be understood or explained, usually because it is very strange or complicated. (事物)不可理解的
For some unfathomable reason, there are no stairs where there should be.
因为某种不可理解的原因，该有楼梯的地方却没有。
ADJ（形容词） If you use unfathomable to describe a person or the expression on their face, you mean that you cannot tell what they are thinking or what they intend to do. (人、表情)莫测的 [文学性]
...a strange, unfathomable and unpredictable individual.
...一个奇怪的、高深莫测且难以预料的人。