Overview
There is an initially small number of purple Lumini at the start of the game, but by using a glitch(?) you can obtain as many as you want. This will make the “Pilgrimage” achievement much easier.
Step One
Collect the energy in the starting chamber and deposit it to get more purple Lumini as normal, and exit the room.
Step Two
Outside of the room, collect the energy from the surrounding rooms. There’s plenty to find but beware of hazards.
Step Three
Go back into the starting room and deposit the energy you collected into the cube to receive more purple Lumini.
Step Four
Restart the game using the “Main Menu” option on the pause screen and then selecting Continue from the main menu. Killing all of your Lumini to get a game-over also works.
Afterwards you will see that you have kept all of your purple Lumini but all of the energy has reappeared.
This glitch can be repeated as many times as necessary to get an unlimited number of purple Lumini.