Story related, can't be missed.
You'll unlock all of the Totem memories one by one after having completed certain areas, defeated bosses and naturally progressing through the story. The very last Totem memory is unlocked after defeating the final boss, 'HIM'. After exiting the memory the achievement will unlock.
This achievement has no relation to the 'Retrieving Memory' achievement as I previously believed. After verifying the ratios here on TA, PSTrophies and Steam it has become clear that this doesn't hinge on rebuilding the Creators' first memory with the Backup Floppy Disks.