Zora Stone Monument

The Zora Stone Monuments are items that appear in The Legend of Zelda: Breath of the Wild. They are stone tablets written by King Dorephan that record the history of the Zoras. There are 10 scattered throughout the Lanayru region surrounding Zora's Domain and a copy of one can be found within Zora's Domain. Some of them have become worn over time making reading them difficult such as the Stone Monument found in Zora's Domain while others survive intact. Some record historical events such as the founding of Zora's Domain, construction of the East Reservoir Lake, the origins of certain Zora traditions, to the life and death of Princess Mipha, to the actions of King Dorephan and Prince Sidon following the Great Calamity, and even a story of how Link drove off a Lynel that threatened the kingdom before the Great Calamity.

Quest
During the Zora Stone Monuments Side Quest, Link is asked by the Zora Jiahto to find all 10 Zora Stone Monuments so he can compile them all in a book. Though their are actually 11 monuments in total, the one in Zora's Domain does not count as Jiahto already knows its location and it is actually a copy of a tablet found on the path leading to Zora's Domain.

Once Link has located and examined all 10, he can return to Jiahto and will be rewarded with a rare Diamond.

Zora Helm
The monument in Zora's Domain provides clues that can lead Link to the location of the Zora Helm. As the tablet is worn, Link must carefully read the monuments text, filling in missing letters and gaps like a word puzzle. Ultimately the monument points Link in the direction of Toto Lake where the Zora Helm can be found. Careful reading reveals a story of how 100 years ago before the Great Calamity, Link once drove off a Lynel that threatened Zora's Domain and during the battle somehow won the Zora Helm which was later enshrined in Toto Lake in memory of Link's heroics. The Zora Helm can be obtained at any time and Link does not have to do either the side quest or read any of the stone monuments to actually find it.