Shadow Orbs are floating purpley spheres found deep in the chasms of the Corruption. If a world ends up generating with Crimson instead of Corruption, Crimson Hearts will be replace them instead, both having the same effects.
Each world that is generated with Corruption will have several Shadow Orbs, and destroying at least some of these can be an important part in game advancement. This can be done using any Hammer, or with bombs or dynamite. Shadow Orbs release a fair amount of their own flickering light, like Demon Altar , and this helps players spot them underground.
Shadow Orbs are normaly located just below the bottom of each Corruption chasm separated from the main Chasm's cavity by some solid Ebonstone, and are also surrounded by Ebonstone on all sides. Mining Ebonstone requires at least a Nightmare Pickaxe . Ebonstone can also be broken up using Dynamite or Bombs, or can be mined with lower-tier Pickaxes by first changing it to normal stone blocks using Purification Powder.