It's been proven that the volcano at the Isle of Fire has a cave that is affiliated with the Guild of Eternal Shadow.

This cave is uncharted, but a captive guild member exposed information while on his death bed. Because of this, we now have a basic sketch of the cave as seen below.



Now the part you're probably wondering about.... how do you get in?
We learned that the cave entrance will only be unblocked with action taken by the Guild. Hidden in Britannia are 4 switches.
1. Each switch must be triggered before the cave is accessible.
2. Each switch is colored with the deep red known to be a color of the Guild.
3. Each switch is engraved by the Guild.
4. Each switch will vanish upon use. One boulder blocking the cave entrance will vanish as well.
5. No switch is in the same city as any other switch.
6. One switch is in a home north of Bay Side Road.
7. One switch is at holy place on an island town.
8. One switch is on a small island a short distance from the mainland.
9. One switch is at the Paladin's Shrine.
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Good luck, the Fire Tunnels await you!