Since then it hasn't booted again (tried raspbian, lite, the bootloader recovery, and alpine).
It turns on with a solid green light, but after a half a minute or so it will begin blinking, and slowly speed up the blinking rate until it "balances out".
Now if, however, I pull the plug and put it back in, it will keep blinking at the speed it previously was, leading me to believe the blinking is tied to the pi's temperature.
Video showcasing exactly what's happening: https://files.catbox.moe/uzybhq.webm
Started with raspbian to test and update, then installed Alpine, the latest of both as of 2-3 weeks ago.3) Please include which distro/SD card image you are using, and which version of that distro/image
Tested with two cards, a 2gb kingston, and a 32gb sandisk ultra class 10, but the blinking happens even without a card inside the pi.
Can't say for sure but it was probaby inside the case when it started.