Generated a new world and started a new fort, using the Masterwork mod.
Struck the earth, preliminary diggings started... then the notice of striking 'foreboding shadow' pops up. I cancel the designation on that tile. The next notice of 'foreboding shadow' I get is when I'm digging out a long 3 tile wide corridor - before I can cancel the designation, my miners break that tile. Straightaway, interrupted mining, and dwarves frozen in terror. I go to check... and out of the foreboding shadow comes a balrog. A large, firebreathing, balrog. Three balrogs, who wreak havoc on my mining team. One miner gets lucky and smashes a balrog's soulgem before dying, so now there's only two balrogs looking for dwarven lunchsnacks.
Off I go to military screen to conscript my latest batch of immigrants, where luckily some came with weapon skills and the weapons to go with them. One of which has a spear, and some skill with spears, who eventually takes out one of the named balrogs. The surviving one goes on a rampage through my dining hall and bedroom apartments, avoiding the speardorf.... and falling to the prototype speargolem pet of one of my immigrants.
Fortress survives, at the cost of 13 dwarf lives.
Masterwork definitely has returned to me the feeling of 'Losing is Fun!'