The level 80 Monolith appears to be named “Fall of the Empire” in both the map screen and the inventory “Blessings” tab’s Timeline selection dropdown, but the associated quest for it is titled “Monolith: Ruin of the Empire”. Album https://imgur.com/a/ccmSoIb has screenshots of both the map/quest and inventory views as of 0.8.4g.
This appears to be related to old bug Typo In Level 90 Mono - #2 (also noted in Monolith of Fate Blessings List - #22 by Athenaise). Based on the screenshots in the latter, it looks like the map used to also read “Ruin”, and the map has since been corrected to say “Fall”, but the quest name looks like it got missed when the map text was fixed.