- Locked Mementos Main Quest
Talk to the researchers at Serenne Stable to accept this quest.
The objective here is to take a picture of the three leviathans in the world.
The last one, the Hebra Great Skeleton, is in the cave with the To Quomo Shrine. This cave requires unlocking. The entrance is by the pond to the southeast, east of Hebra North Summit on the map. Place two Cryonis pillars in this pond, and head east uphill to the snowballs. Roll one downhill, across the ice pillars, to bust open the door to the cave.
Return to the researchers. Talk to them individually to hand them each of the three pictures. When all three are turned in, the reward is a gold rupee.
Akrah at the Serenne Stable asked you to get a visual record of the leviathan bones. The record need not have the whole skeleton in it, so long as the skull is visible.
Leviathan bones are apparently found in Eldin to the northeast, Hebra to the northwest, and Gerudo to the southwest.
You took pictures of the leviathan bones in Eldin, Hebra, and Gerudo. As thanks for advancing the cause of paleontology, Akrah gave you 300 rupees.