In Chapter 3 Skies of Vengeance, there is a way to get unlimited yellow orbs. First, get the key card on the lower level.

Save your game by going down the one of the spiral staircases off the Main Deck. Now, head back to the beginning of the game.

At the end of the hall in the Living Quarters there is a door that requires the key card. Make sure you have a few Elixirs of Spiritual Life before you enter. Kill as many enemies as you can without dying, then exit through the door.

Save your game, restock your elixirs at the shop (it is located at the other spiral staircase of the Main Deck) and repeat. Once you have all the upgrades that you can purchase at this level, you can just stock pile as much Yellow Orbs as you like.

Submitted by Cueball1897 (cue_ball1897