My first couple of fortresses played it safe and nothing much happened - dug out a bit, traded a few times, got a couple of waves of migrants, got bored, started another one -- but this time, having tried my hand at modding, I started a quick test fort (well, that was the idea) in an area with an aquifer, so that I could play with pumps.
As I discovered once I embarked, the area also has a magma pipe coming right up to the surface. Score!
And then the fire imps came out and started taking potshots at the local wildlife.
The first time they set the world on fire, the merchants from my newly-modded-in land octopus civilisation spawned right in the middle of the conflagration. (note to self: fix them so they don't leave bones...)
That was pretty awesome, but the second time wasn't as amusing as the first, so I decided to have my first pump trial take water from the level with the sand (right next to the magma pipe, score) and see if that would solidify the top of the magma pipe.
While I was building the windmills to power the pumps (and disassembling, and rebuilding again so they would work properly), the imps started another fire. Somehow none of my dwarfs caught fire, even though they were pathing right through it to get to the windmills.
So now after a couple of false starts the pumps are running (and overflowing, and threatening to flood my fortress if my masons don't put the barriers up in time), water is flooding the surface in every direction by the magma pipe, which is solidifying where the water hits it, and then it keeps caving in, and there's mist and steam everywhere, and oh yeah, the other side of the map is still on fire.
My FPS is not happy, but this is the best fort I've had.