By far the fastest way to get this is to choose Armory Pod on Too Easy. This pod starts you off with every type of weapon, and hero fighting stats are greatly enhanced, making it easy destroy mobs without any minor module assistance until maybe floor 4 or 5. Rush through doors as quickly as you can, making sure mobs don't get past you and hurt the crystal. When you get to a point where mobs are larger and tougher, abandon the game and start again.
My favorite team for this is Ken, Skroig, Hikensha, and Golgy (high speed for crystal running).