phantom group

例句：

1. 1. The phantom group was a secret society that existed only in the minds of its members.
   这个幽灵群组是一个只存在于成员心中的秘密社团。
2. 2.The phantom group had been active for decades, but their true purpose remained a mystery.
   这个幽灵群组已经活跃了几十年，但他们的真正目的仍然是一个谜。
3. 3.The phantom group was rumored to have been responsible for several unsolved mysteries.
   这个幽灵群组被传说是几个未解之谜的幕后黑手。