Talk to Thane | The Fire of the Mountain Darksiders 2 Guide

Head back to the northern part of [Tri-Stone]. You should find Thane on the upper balcony, but before you talk to him you can also have another conversation with Eideard. Wait for Thane to unlock the passage, and take it.

[TIP: You can return to Thane and any other Ancient present in this location any times you want, and it's best to use fast travel for it. To do it, open the world map (O button, fourth tab) and select Tri-Stone.]