Niche D20This variant rule helps reduce the amount of dice rolls needed in combat to help expedite things especially if the rolling is not automated within some software.
When doing static defenses first decide if you wish to simply apply this to basic mobs or all creatures. When applying to basic mobs this generally means any basic creature that is not a boss encounter for a party, this keeps players rolling their defenses as normal, but reduces the work the GM needs to put in to get through an encounter; its generally recommended to let the boss monster still roll for its defenses to give players more varied results, as it might feel more fair if they still must roll for their defenses. If applying to all creatures then simply apply this rule to both players and NPCs.
To do static defenses simply treat the roll for all CMD, Saving Throws, and AC rolls as if they had rolled a 10 on the dice every time. This will cause creatures using this to seem more consistent in their defenses, leaving much more of the random chance on the attacker.