This achievement can be unlocked by completing any tomb, but is easily done in the prologue of the game during the side mission Hideaway. This mission takes place in the Mountain of the Dead Tomb in the northwest region of Siwa. Here, outside a cave, you'll meet a boy who has lost his brother. Once you enter the tomb there's plenty of loot to find, but what you need for this achievement is to interact with a stone tablet in the room you find the lost brother in. Do this, and the achievement is yours!