The Crypt of Joy fell really fast. It was a fortress in the Joyous Wilds one world map tile from two necromancer towers. We had about 25 dorfs, including one necromancer who I was a little excited about seeing in action, so I sent him to the military.
6-9 months in we got sieged by the undea. I forgot to make defenses and hadn't found metal yet. So I locked the hatch and turtled. Then I noticed my farm screwed up, not sure how. Plumps were set to brew only and for somehow we ran out of spawn. They also weren't getting put in barrels for storage and they all started withering. Then we ran out of drinks.
So I quickly mined until I found water in the second caverns, opened it up immediately was attacked by a croc. I have no clue how it got there so fast, it was literally in the freshly opened path, which was not close to water. My unarmed, unarmored military was sent down to die for their brethren, which they did. The necro then brought one guy back as intelligent and everyone else's body parts back as zombies. The intelligent killed the croc and the necro brought it back as a zombie, presumably to fight all the zombie arms that were everywhere. 95% of the fort died trying to run past the croc to water, or to get back into the fort.
I eventually managed to get the IU back into fort while the zombies chased cavern life. Where he sat with a bard for months until he died of thirst. Then a migrant wave showed up, I attempted to lure them into the fort by unlocking the hatch which magically the zombies got into unseen while I watched, killing my only undead soldier.