This is the 6280th most frequent Korean word.
신비한
"신비한" means "mysterious" or "magical" in English.
In this case, '신비한' qualifies the story as being mysterious and likely fascinating.
어릴 때 읽었던 신비한 이야기가 아직도 기억에 남아.
I still remember the mysterious story I read when I was young.
The word '신비한' is used as an adjective describing the forest as having mysterious qualities.
신비한 숲의 안에는 숨겨진 비밀이 가득하다.
Inside the mysterious forest lies a plethora of hidden secrets.
Here '신비한' describes the atmosphere as mysterious and intriguing.