For this achievement you must collect all 5 Moura's Tears as well as find all the "main" secrets and a few other things.
Here are the items you need to accomplish:
1. Break Tolomeras Curse-Honestly, I'm not sure what this one entails as its always checked off for me. I believe this is for collecting the five Tears and getting the good ending.
Check my solution for Tear locations:
2. Save the Amadis from the flamesVery simple to get, during Chapter 3. Refer to solution for location
3. Invoke the Lady of the LakeFound easily during Chapter 4. If you die and lose the fire sword, it has no bearing for this secret.
4. Be kind with the SirensYou cannot kill the Sirens during the play through (they look like Mermaids). They only appear in two sections, so not to tough. Just make sure you dodge them and don't kill any of them.
5. Meet the Gamusin PeopleBefore fighting the Turtle boss there will be a chest with a Crystal Ball, make sure and pick this up. After killing the Turtle a section will start with a creature guiding you with a torch. Drop down the first chain and head left, you will find a small village with the Gamusin People. If you die any time after picking up the Crystal Ball you will not be able to get this, if this happens you can exit out and restart the level to try again.
6. Find the Hidden ScrollAfter getting all 5 Tears and entering Level 8, make your way through until you get into the castle. You will fight the caterpillar boss and a few enemies. You will eventually drop down into a room with two headless knights, kill them and head right. The far right pillar has a small cross on it, crouch down under it and the Scroll will appear.
7. Use no ContinuesThis is pretty self explanatory, you cannot use a Continue, at all!
There is a trick to it, at any point during the level you can quit to Main Menu. This will give you the basic sword and all your lives back, but you will start at the beginning of whatever Chapter you are on. Doing this you can essentially die as much as you want, but when you lose your last life you quit out, then try again. Have fun with Chapter 8 :)
Be aware when you quit out, don't forget to collect Tears / Secrets again! I messed up once on this as I forgot to collect the Hidden Scroll on Chapter 8 again and it cost me the achievement.
Once you complete the game, after ending cutscenes you will get a checklist shown to you. All must be checked green, shortly after the achievement will pop!
vSully has provided a snapshot of what your final screen should look like: