The Sojourn

Once you've completed the first set of main challenges (every part of the star emblem will light up), you'll approach a castle that's building up as you enter. Don't enter it.

To the left and right are bonus challenges - is Mesmerising Symphony, is Triumph. It's up to you to choose which one you want, but video walkthroughs of both levels exist anyway and I'll link them here:

Mesmerising Symphony:
Triumph:
The scrolls collected at the end of the level are Merits of Life. The achievement pops once you read what's on them.