Mortal Shell: Enhanced Edition

As the description says, you have to spend 100K tar in Virtuous Cycle. The only ways to spend it are: at the Runic Gate (where it'll all most likely go), the three lutes, pillars, or temple entrances.

I don't recommend the lutes since they are wildly expensive. At least, get them after you've got everything out of the Gate. I do recommend that if you're at a loss on what to spend your glimpses, then spend them on Tar Retention (or whatever it's called) which allows you to keep your tar at varying percents all the way up to a maximum of 100%. Each percent is 2 glimpses so that would be 200 glimpses in total to keep all of your tar. Dumping all of your tar into the Runic Gate upgrades is most efficient if you're going for the other achievements in the DLC as well.

As long as you get close to finishing cycles and spend your glimpses/tar after each area, you should get this within 6 or so cycles.