1. First of all, the Ladon Gesa legend needs to be obtained by forgetting the relics and opening the treasure chest.
2. Secondly, there is a treasure chest at the forgotten relic 304 and 155 in the above picture. After opening it, you can get books about the legend of Gesa in Ladon.
3. After finally getting it, you can get a diamond reward by answering the question 10 correctly.