For this achievement, you must collect all five Moura's Tears and complete the game without having died after receiving the Fire Sword from the Lady in the Lake near the start of chapter IV.
There are no real shortcuts here other the fact that you can die and continue up until getting the Fire Sword. And if you die during chapter IV, you can quit to menu and continue from the start of the chapter to try again. After completing chapter IV, you MUST play through the rest of the game without dying. This will require knowing chapters V through VIII very well, so practice the hell out of them. Know where and when enemies appear and how to best engage the bosses.
I struggled most in chapter VI the Aqueduct as there are so many places to get hit and knocked off a ledge to instant death. It's tough to get good practice in as you lose your Fire Sword upon death so continuing so you can practice will cause you to use a different weapon. The Fire Sword is powerful but handles much differently than the Sickle, which was my preferred weapon.
Other potentially problematic parts:
• the moving platforms in chapter V
(shown here)• the downward part with bubbles near the end of chapter VII where you must make a jump and shoot a bubble midair
(shown here)• the second section of chapter VIII near the large beached ship when you have to deal with imps and shield knights
(shown here)• the final upwards section of chapter VIII with the skeletal mages and fire bats
(shown here)• the final boss
(shown here)Practice, practice, practice. Then practice some more.
Here is a video showing chapters IV - VIII of my successful run:
Good luck.