Safe and Sound is an optional mission in Borderlands 2 given by Marcus. It becomes available after Rising Action is complete. While heading up a flight of stairs, the safe will be shown as being accidentally dropped into the Caustic Caverns. After locating the safe, a giant crystalisk named Blue will appear. Blue differs from normal crystalisks in that it can generate juvenile exploding crystalisks that can pursue characters into places where it can't follow. Blue also has a ranged shock attack that can quickly drain shields.