Scleroderma citrinum
Mushrooms known as puffballs   are commonly divided into two groups by people who eat fungi: Puffballs with a pure white interior are generally considered safe to eat, while puffballs with dark interiors are not edible.  
The coal-black interior of Scleroderma citrinum, an occasional summer find on soil or around rotting wood throughout Illinois, leaves nothing to doubt in this black-and-white decision.