When I attempted to enter the ruins, the game crashed. This is a 6000+ day save. I opened up this particular ruins entrance about 1000 days ago. I've been in and out of the ruins regularly since then. I don't have mods enabled.
The crash error message (see below) references nightmarelight.lua.
The log file is attached.
I'm hoping there was a recent update that introduced the error; otherwise, I'm probably screwed.
1. Open up a ruins entrance. 2. Have fun in the ruins for 1000 days. 3. Attempt to go into the ruins 4. Sorry. No can do: ERROR