Hunt dark blood vespers around the Ashwood Trench to acquire vesper's black bloods. Then, go to the Altar of Sahrar and talk to Luis Garcia. Use your quest tracker to see your progress.
Chris Wincott: Hello Aitan! NakanoAzusa: It's surprising to see a merchant here? Chris Wincott: Yes True merchants travel to anywhere where Chris Wincott: customers are, right? NakanoAzusa: This is a dangerous area even for the Aitan. NakanoAzusa: Business is important but your life as well. Chris Wincott: Haha, no worries. I'm not a military merchant Chris Wincott: but almost. This is the only store nearby. NakanoAzusa: True, we do need a store. HiiragiKagami: But aren't you scared of this place? Chris Wincott: I am indeed. That's why I have a Chris Wincott: favor to ask. NakanoAzusa: What is it? Chris Wincott: My troubles are not just one or two, but first would NakanoAzusa: be the air. The ashes in the air! Chris Wincott: Even wearing the mask doesn't seem to work very well. Chris Wincott: If a physical way doesn't do it, I shall try spells. NakanoAzusa: How? Chris Wincott: So I studied a bit. If you gather the blood of dark blood Chris Wincott: vespers and make a medicine, it should work. NakanoAzusa: But who could make that? HiiragiKagami: There's only one scholar here. If Mr. Garcia HiiragiKagami: doesn't know, then who would.