The Crystal Ball is a Treasure found in Jailbreak of Sly 2: Band of Thieves. It is booby-trapped, so Sly has to bring it back to the Safe House before time runs out. Once at the Safe House it can be sold on ThiefNet for 504 Coins.
It is a large ball of crystal sitting on a shaped gold or bronze base. Attached to the front is a booby-trap.
It is found in the fence of the same building the "Code Capture" job is.