This page contains a detailed description of Treasures of the Past bronze trophy in Shadow of the Tomb Raider. This achievement is obtained by deciphering one of the monoliths.
Monoliths are stone tablets that you can find in different places in the game world. They are one of the secrets and are marked with unique icons on the map. The first object of this type can be found while exploring the Peruvian jungle, but you don't have to look for this particular monolith - to unlock the trophy you can use any of your choice.
In order to decipher a message written on the monolith, Lara must be sufficiently familiar with the relevant dialect. The requirement for the level of dialect knowledge depends on the monolith. For example - in the picture above, a good knowledge of the Mum's dialect is required.
There are 3 different dialects in the game -Mam, Quechua and Yucatec. Each of them has three levels of knowledge and you can check the current level in the artifacts tab -this is shown in the picture above. You can learn dialects by finding related murals and treasures.
Note -After deciphering the monolith, you have the opportunity to complete the related puzzle, but this is no longer required to get the described trophy. You will unlock the achievement when you read the message written on the monolith.