post #5018742

A natural 1 (or sometimes called a "nat 1" for short) in d20-based systems refers to rolling a 1 on a 20-sided die. This typically gives a critical failure on certain rolls, like attack rolls or saving throws. (The exact mechanics depend on the roll being made, the version being played, etc.) Outside of d20 systems, a nat 1 may simply refer to an instant or guaranteed miss/fail.

The opposite is rolling a natural 20, or critical success.

See also

• d20
• gameplay_mechanics