Soul ReaperG 20

Souls from crystals don't count towards this achievement when you break them. You have to collect the souls when you kill enemies, items... and when you re-collect the souls you left as a soul-cloud when you die

So, you can use this mechanism to count the souls stored into crystals: if you break crystals, the souls inside are added to your total and, more important, are added in the soul-cloud you left when you die. So, if you go back where you die and collect this soul-cloud, you collect the souls previously in crystals.

To obtain this achievement really quick, it's easy : when you have sufficient souls in crystals to have around 100 000 souls, just break them to add them to your current counter (bottom-right of the screen). Then, go to a spot with some weak enemies (like South End or Corssroads). Let the enemies kill you. When you respawn, collect the soul-cloud, you have collected 100 000 souls! Just repeat the process (die, respawn, collect...) until you unlock the achievement. If you start the process with 100 000 souls, you just have to reapeat it 10 times.

Having 100 000 souls in crystal can be a lot at the beginning. But I just revisited each location after the 3rd hollow, I gather 75 000 skulls in crystals.