So I tried playing as humans in a Terrifying biome for a challenge, and before spring was even over I had to kill the fort because I was getting 15 FPS. I don't know why. No more than 10 undead showed up and all got murdered by the swordsman I brought. My miners were digging out a large area underground to hole up in while I figured stuff out, but it was nothing truly crazy and I still only had my original 7 + about 15 animals. I've had WAAAAY bigger projects in dwarven forts with >50 FPS, so I was pretty well scratching my head wondering wtf was going on.
Anyone have an idea what caused it?
FYI I was playing on a 3X3, small world, multi-level viewing off, and with cavern facehuggers off.