Shadow Keys are from the game Dragonball Xz: Dark Smog. There are five of them. Each of the dark FIVE hold one of the five Shadow Keys and must be defeated by a different playable Saiyan to proced. They are used to unlock the way to dark TRUNKS. They are the crystalized soul of the member of the dark FIVE aftyer they are defated. During the final fight, dark TRUNKS absorbs them to become dark DARK TRUNKS instead of the dark FIVE's corpses.