ACCESS THE CRYPT
During Chapter 6 – Return to Hidden City you must rescue Unuratu from the Kukulkan prison. As you cross over the river below along a tethered rope, the story objective continues to the right, but to the left is the entrance to the crypt. If you’re coming back to this crypt later, fast travel to the Temple of Kukulkan Base Camp.
Drop off the tethered rope next to the mural and climb up the left cliff, then jump from the protruding rock to the handhold and shimmy left until you can climb up. Inspect the mural on the right before heading up the steps and crawling through the tunnel to get inside the crypt.
FIND THE SARCOPHAGUS
Follow the corridor into the next room and jump to the craggy wall ahead. Rappel all the way down and drop into the cavern below. Head forward through the door and follow the tunnel through a narrow opening and into the next room. At the other end is a barrier, so pull it down with a rope arrow. Head through the doorway and follow the corridor left and through another narrow opening.
You can head left here to dig up a survival cache, then go up the steps and jump to the craggy wall on the left and scale up to the top. When you reach the overhang, rappel down and swing over to the gate. Push the switch to open it, which will flood the cavern.
Now follow the path through the archway to find the sarcophagus. Loot it for the VESTIGE: CH’AMAKA’S WAR VEST.
EXIT THE CRYPT
Return to the previous cavern and dive into the water. Fast swim all the way through the tunnel, making sure to take a breath at the air pocket, until you can resurface at the end. From here, simply follow the path until you’re back outside.