Wik: Fable of Souls

Challenge Mode requires you to play through a series of puzzle-like levels independent from the main story mode.

As you progress, your completion percentage in Challenge Mode will be displayed on the menu screen. Though the Achievement states that you must finish 30%, that's not entirely true. The Achievement will unlock sometime shortly after you hit the 30% mark, so don't be discouraged if it doesn't unlock right away. Clear two or three more levels and it's sure to unlock.

Each challenge level has an option to show you the ideal solution, so if you get stuck you can always get a hint. You still have to pull it off, and some of them can be a little tricky, but at least the thought process can be streamlined in this way.

Just as a side-note. Make use of the skip feature if you are going specifically for this achievement. If you get stuck on a level, skip it and come back to it later. 30% isn't too hard to get.