Type of riddle: type a poem.
A: One of them-they call it forever true.
From: Song of Eternal Sorrow by Bai Juyi in Tang Dynasty
The original sentence is: he is looking for one of them-they call it a real person forever, with a snowflake face like her. So he went to the golden gate of the West Hall, knocked on the Jasper Gate, and asked a girl named Small jade to tell Shuang Perfect.