Dark Gun Pieces

Dark Lens:
Complete the game once

Phantom Frame:
Complete the game twice
Chaos Battery:
On Hard difficulty complete the game once
Information Room
Complete the game once and save it. Start a new game and on the saved file of the completed game you will come upon a Solar Tree which will have a wap next to the little hill going up to the raised area. To be teleported to a small room with five Hint Blocks which has information about your game data you have to access the warp.
Pink Solar Tree
Gather at least 1,500 Sols to get the Pink Solar Tree.

Astro Battery:
As the evening turns to night look at the Pink Solar Tree.

Chaos Battery:
Obtain the Pink Solar Tree and complete the game on Hard mode.