For this achievement, you need to find all 3 Beatrice stones

If you miss the original location, they will appear again in other fountains you encounter later on in the game. If you did not complete this in your first playthrough, you'll be able to find the remainder of the pieces you miss in the exact same locations you found the others before.

'Backup' Locations:

-Anger: Do not drop down to a big circular platform, but continue along the cord to find an orange fountain.
-After the mirror maze area, you'll climb down a wall with several fire spouts. After you get to the bottom, you'll be in an area with mana and health fountains. Jump up to the alcove to the right. Then jump left across the gap. You'll see an item fountain behind you and one further ahead. You have to jump kind of around the wall to get to the one further along, which has the stone in it.