I've hit 500 years on the 1000 year challenge and can't figure out how to progress. I've got 750 time crystals from earlier runs, but I can't figure out how to shatter them - I wasn't given the option to build Ziggurats anymore when I reset into the challenge. I can't make relics or trade with the Leviathans to get relics. How do I research Tachyon Theory and Chronoforges?

 Sorry if I'm just being dumb, but how do I combust time crystals? I don't see the option on the Time menu when I have more than one time crystal. Do I need to research something first? Is it in a different menu? I'm playing v1.5.4 on Android.