Constitution checks are uncommon, and no skills apply to Constitution checks, because the endurance this ability represents is largely passive rather than involving a specific effort on the part of a character or monster. A Constitution check can model your attempt to push beyond normal limits, however.

The GM might call for a Constitution check when you try to accomplish tasks like the following:

• Hold your breath
• March or labor for hours without rest
• Go without sleep
• Survive without food or water
• Quaff an entire stein of ale in one go