Finding the Dark Soul Easter Egg is simple, head over to Caimanes Bravo Rally Point. After you spawn over there, run towards the main road ahead and go a little bit to the right as you cross the road so you can run up the hill in the trees.
And that is all to this Easter Egg, nothing long like the 3 Witches or El Yeti. No reward, just a plain old Easter Egg.
If you have collected all of the Kingslayer Files for Caimanes Province, you have visited the area “Child Hut”, you may or may not have noticed the Ghost Child standing in the open before running into the bushes and disappearing. You can revisit the Ghost Child to see him run into the bushes. Approach “Child Hut” found on the TacMap in Caimanes Province how you please. Fly in fast, you can catch him with Photo Mode before he starts to run. Approach the area slowly, you’ll miss him.
There is a Kingslayer File for this myth, the file is called “The Boy that turned into a lake”, and on the bottom of the list. Kingslayer File reads: “People from the eastern village of San Ignacio de Moxos say that, a long time ago, local women could only use a small swamp to wash clothes and men had to go fishing miles away. One day, a young boy went to help his mother and as he walked into the water, he mysteriously disappeared. His mother ran in the village to seek help. When the villagers reached the swamp, the boy was nowhere to be seen. Nowadays, the swamp has turned into a beautiful lake full of fish and clean water.”
No reward or anything, just interesting real-life mythology Easter Egg. “The Legend of Isireri Lagoon”.