I did something extremely stupid. I'm currently working on a 10.04 system (work-related), and since I was missing some fonts I decided to simply copy some over from my own, 12.10 system. I ran
cp -R <12.10 root>/usr/share/fonts/truetype/* /usr/share/fonts/truetype/
Immediately, terminal and window header fonts got completely messed up, although chromium still shows everything correctly, as does nautilus.
How can I restore this directory? Is there anything else I have do afterwards?