Armor Class (AC) and Magic Cancellation (MC) - hyvanmielenpelit/GnollHack GitHub Wiki

Armor Class (AC)

Armor Class (AC) is a value that determines how easy it is to hit the target.

AC starts at 10.
AC decreases when you get better armor. So, the lower the AC is, the better your Armor Class is.
AC below 0 also provides damage reduction for players.
AC can go even as low as -100 (or even lower) with certain equipment setups.
AC calculations are different for player characters and monsters.

For exact formulas involving AC, please visit the Armor Class entry in the NetHack wiki.

Magic Cancellation (MC) determines how easy it is to inflict a certain magical or semi-magical effect on the target.

MC starts at 0.
MC increases when your resistance to these attacks improves. So, the higher the MC is, the better the resistance.
MC usually varies between 0 and 25.