Encounter Design: Have ways of attacking different player defenses

An issue that I’ve read about quite a number of times are GMs who take issue with players who stack high amounts of AC, usually a Fighter or a Paladin in plate. Specifically for 5th Edition D&D, between the Defense Fighting Style, Splint armor, and a Shield, a character can get 20 AC, which is enough to let them avoid getting hit more than half the time until at least level 10. And then there’s still one more point of AC-in-waiting from Plate armor, plus whatever magical items the player might acquire.

The solution, of course, is to attack something else besides AC, namely saving throws. A Fighter might be weak against Wisdom saves. A Paladin might be weak against Dexterity saves, and so on.

That’s the core of this idea: in any encounter, always have a way of attacking different defenses. For 5th Edition, the key points are AC, Dexterity saves, Constitution saves, and Wisdom saves. In an encounter with four monsters, you might want to have two of them being capable of attacking against AC, with the other two capable of attacking against one other save (but don’t be afraid of throwing in the occasional Strength or Charisma save curveball, either!).

The added wrinkle is that pulling this off might require some homebrew. A lot of monsters in the Monster Manual are either straight melee attackers, or if they have a ranged attack option, the bow or sling or whatever is also attacking against AC, and that’s no good.

Even when you get to the odd spellcaster, the particular way that D&D does it spells still doesn’t always jive with what we’re trying to accomplish:

• some spells are debilitating, debuffing, or otherwise have rider effects instead of being straight damage
• some spells that are straight damage then use spell attack rolls, which are no good because they still target AC
• spells that are straight damage and target a saving throw, either deal too much damage to be used multiple times within a fight, or literally can’t be used multiple times within a fight, because of a limited number of spell slots

So in order to achieve the effect that we want, you might need to create all-new “basic attacks” yourself.

As an example of what I’m describing, consider the very first fight of Lost Mine of Phandelver: four goblins. They either have a melee attack against AC with their scimitars, or a ranged attack against AC with their shortbows. A freshly-minted Fighter can start that encounter with 19 AC from their Chain mail, shield, and Defense Fighting Style, which would give the goblins roughly a 30% chance of hitting them.

While I’m not ruling out trying to attack someone else, what you might want to do on top of that is to turn one of the goblins into a Goblin Sharpshooter with a 30-foot Sling attack that deals 1d4-1 piercing damage on a failed DC 11 Dexterity saving throw. And then turn another goblin into a Goblin Skullrattler with a 20-foot Shadowblight attack that deals 1d6 necrotic damage on a failed DC 10 Wisdom saving throw (half damage on a successful save).

As a GM, this gives you more options on who and how to attack. On the other side of the table, the players then have some more interesting tactical choices to ponder.

For older editions, the same principle broadly applies: between AC, Fortitude saves, Reflex saves, and Will saves, give yourself the option to hit two, and as many as three of them, among your different monsters.