Fire and Brimstone

Koh is in the Smithing outlet store in Mhaura. The hunter shows up and la de da you're off to the Necropolis… eww. I rather enjoyed the cutscene though.

Enter Eldieme Necropolis via the southernmost mound in Batallia Downs (past the weapons). You'll get a brief cutscene as you enter. You're headed to G-9, the monument thing by the southern grave room. If you don't have a map you can just make all left turns until you get to that grave room. You can sneak past all the undead but there are doors in your way - so you might need a teammate to operate the switches. One Azer (bomb type) guards the monument. They detect by sight but you can't read the monument while invisible so I recommend waiting for it to go behind the monument. There's another cutscene when you check the names on the stone.

Next head back to Windurst for a Conversation with Perih. She sends you to Oztroja Castle (East side of Meriphataud Mountains).

Head to the third floor of Castle Oztroja, the pool with the leeches, at H-9. To get there go east across the first floor to Door #1 (with the trap to the basement, which you're probably familiar with from Stones of Power). Then travel west across the second floor and through the combination door. The pool room is just beyond that.
This room has yagudo (VT to lvl 50) around the pool and leeches inside the pool. Yagudo aggro to sight and leeches to sound. You can scavenge while sneaked but you will become visible as soon as you use this ability. For this reason you might want to bring friends to clear out the yagudo, at least on the half of the room near where you entered. Try to be in the exact center of the pool when you scavenge, and be aware that it will likely take multiple tries. You can leave as soon as you get an Old Earring.

Back to Windurst again, trade the Old Earring you scavenged for to Perih for a final cutscene and the Hunter's Beret is yours!