Monoliths in Shadow of the Tomb Raider are used to unlock special treasures. These treasures are buried in the ground and cannot be extracted if you don't get hints from the monolith. Each treasure provides supply experience points. Monoliths also count to Shadow of the Tomb Raider in 100%.
Monoliths can be found in various places on the map. They look like stone tablets and are marked on the map with a special icon. In the screen above we have shown how the monolith icon looks like.
To read a monolith you need to know the appropriate dialect at a given level. The level of dialect knowledge depends on the level of the monolith. In the early stages of the game you must have about 50% dialect knowledge to read a specified monolith.
There are 3 different dialects in the game. Each has 3 levels. You learn them by studying chapels and gaining treasures.
After reading the monolith, you will get a hint, and the map will show the area where the treasure is located. The treasures are usually very close to the monolith. It is often enough to just climb up or look at an object (e.g. a statue) and you will find the treasure you are looking for.
Some monoliths are more difficult to read not because of the dialect level, but because they are specially protected. To unlock a way to some monoliths you need to use a shotgun, knife or a fire. This means that in the early stages of the game you often have to give up discovering the secrets and then return to selected location and unlock the monolith.