Natural 1

A Natural 1 indicates a roll of 1 on a d20. A Natural 1 on an Attack Roll automatically misses, even if the target's defense is so low that the attack would hit normally. Additionally, if a Natural 1 is rolled in an Opposed Check, the roller of the Natural 1 automatically loses (unless both opponents roll a 1, then the contest goes to the higher result as normal).

Alternatively, a Natural 20 on an attack always hits and always wins an opposed check.