Also known as the West Mines, the Thunder Mines are named after the sound of the waterfall that crashes down into the chasm these mines were built up around. Invisible from up here, the bottom of the chasm is actually where the dwarves who built this city first arrived and had left their Earthships during the war against the elven empire.
Like the Hematite Mine posted on Tuesday, Thunder Mine is mapped at a scale of 1 square = 20 feet or 1 inch = 100 feet.
This section of mines is currently home to the Brotherhood, a group of nearly mute humans (?) who all look almost identical (except those who have visible scarring or other environmental deformations). The brotherhood seemingly crawled out of the mud one day and began attempting to reopen these mines and are moving the small amount of ore they have collected so far up to the hall of iron where they intend to smelt it down.
Exits from this level are to the right (leading to the East Mines / The Hematite Mines), the top of the page (leading to the Flooded Mines), a set of stairs and an elevator in the upper right side that lead up to the Hall of Iron (and the elevator leads even further up to the Hall of Bronze and the City Gates) and the chasm which leads down to the Earthship Docks.
The Earthship Docks (and the bottom of the chasm in the Hematite Mines which are home to the Gimchak Spiders) will probably not get detailed in this series of Mega Delve maps – the goal of this set is to detail everything at the level of the dwarven mines and above leaving the lower levels for their own development once this is complete and I’ve taken a rest from the whole Delve for a bit.
While the Hematite Mines were designed to feel like a real-world coal mine with large straight tunnels and many side branches dug out into the rock to harvest the main ore veins, the Thunder Mines are meant to bring home a different vision of mining more like that shown in the Hobbit movies when they show the dwarves mining along deep natural vertical shafts seeking precious stones.
This level also finally shows us hints at how the elevator room that accesses multiple levels of the dungeon operates – powered by a water wheel and a series of huge gears. Anything more detailed is up to the DM to determine as it is basically dwarven magic beyond that.