A gremlin made my volcano erupt. Fortunately, the fort is fine, as it was a relatively minor eruption. Not so fine for the king, however.
Here's how:
First, I dug out ten large cisterns between the third caverns and magma sea. It took 25, yes, twenty five, legendary miners several in game years to dig out all 10 of these cisterns. Each one is 20x20 and 65z tall - so, 26,000 cubic U with a total capacaty of 260,000U. These cisterns have their corners touching and thus are interconnected. The bottom of the cisterns are not flat - each one tapers down to a small 5x5 point in steps designed for optimal drainage. Each of the 5x5 areas is drained by 20 pumps.
This is the most complex plumbing job I have built. I've only finished it a few weeks back, but I'm not done with the fort so the save is not yet available. Soon. It's slow building at 3fps. The clown tent certainly isn't helping matters either - I'd probably gain 2 or 3 fps by clearing it out.
This consists of:
1,890 pumps.
2700 gear assemblies
approximately 12,000 tiles of axles
750 water wheels
160 levers with over 400 connections
17 bridges
making for 50,900 power required with 75,000 supplied.
Then I drained my volcano into them with the assistance of 10 pumps in parallel and a stupidly large battery of water wheels.
I also set up a large number of taps to drain portions of the magma sea at strategic points. After about two in-game years, the cistern was full.
Then, I floored off the base of the volcano and proceeded to move my fort into the volcano by constructing everything in there.
At which point I refilled the volcano up to its top.
The magma cistern was full, and so was another large one built of constructed walls on top of the fortress. This one is used to power my magma land mines.
The two rivers on the map are floored over, for the record.
Well, the cistern for the magma land mines has a great number of pumps constantly topping it off to maximum !!pressure!! and capacity. It's a good thing too, because many land mines being activated at once (there is a very high density of them) drops the level noticeably.
This tank also contains a drain just downstream of the pumps for maintainance / expansion reasons.
This drain is sealed off by a floodgate.
This drain pours into my volcano, just below the surface level of the lava (3z down).
A gremlin pulled the drain lever.
Fun was had. The king had just arrived on the edge of the map and got magmaed.
Deliciously.
He was walking along the crater rim heading to the fort when sud--- HOLYSHITWHEREDIDALLTHATLAVACOMEFROM
The king got trapped on an isolated 3x2 rise with the lava rising around it. Too bad for him, it exceeded 7/7 depth in that location because it was in a ravine.
Lava was cascading down the mountain, burning the forest and killing my
FPS* even moreso then the magma land mines did. And I was enjoying every second of it.
*Who are we kidding? My FPS is already dead, the last in-game year took almost a week of actual play time.
The gremlin was killed and the lever reset, sealing the drain again. It was too late for the king.
I have sense invested in anti-gremlin measures, including a massive chamber full of 500 or so levers which drop a small 3x3 portion of ceiling onto themselves when pulled.