I'm at my third now, the first was a training fortress, lots of soil, metals, etc., a river, trees, calm enviroment, flux, no aquifer, the perfect training grounds. My personal garden of Eden. I followed the wiki tutorial and learned to play. After that I experimented a bit, I made it goblin-proof and built things like an aquaeduct [sic] for my hospital and got magma to my forges. Then nothing more happend and I got bored.
So first death is due to boredem.
Second fortress on a glacier, medium evil, high savagery (untamed wilds). Thought it might be more challenging, but it went too well. Got an artifact steel battle axe (160k) at the end of the first year, along with a legendary weapon smith. The created wealth drew lots of good crafters to my fort which created even more wealth. Pierced the caves at z-level 12! The only attack in two years was a beast single-handedly killed by a caravan guard. Then some minor ambushes, that was it. After three years I got so much stuff and dwarves, dug over 250 z-levels deep through 3 caverns that my fps dropped too much.
Second one died of low fps.
So after all the cold on the glacier I sent my dwarves on vacation in a sunny spot: the middle of the desert, scorching heat and terrifying surroundings. Should be fun!
Is there maybe a mod to make the game more challenging? Imho it's too easy once you figured out the basics. I found nethack to be harder.