Active defense in D&D 4e: a thought experiment

Jeremy Baldwin (I think) asked on Twitter: “What if players did ALL d20 rolling? Attack and defense vs. static monster attack values?” He also wrote a blog post on the topic. The ICONS superhero RPG uses a system in which players do all the rolling, and it works just fine. It gives players a sense of actively defending against attacks, and puts more of their characters’ fates in their own hands. You’ve got nobody to blame but yourself if you roll low, and all that. It’s very simple to convert standard D&D’s passive defense model to an active defense model of the type Jeremy describes.

I’d like to take this “active defense” idea a step further by showing just how easy it would be to incorporate this into D&D 4e right now, and how it could potentially improve in-combat role-playing.

In standard D&D, each character has four defenses: armor class, fortitude, reflex, and will. Each defense is calculated as 10 + 1/2 level + other modifiers. In the active defense variant, each character has four defense bonuses, calculated as 1/2 level + other modifiers. Attackers “take 11″ on their attacks, so that their attacks are static figures of 11 + relevant bonuses. So, for example, the warforged barbarian/paladin Alard has an AC of 26 in standard D&D; in the active defense variant, he would have an armor defense of +16.

An attack on Alard by an ironskin warrior minotaur (from Monster Manual 3) might go something like this in standard D&D:

DM (me): The minotaur swings his greataxe at you. (The attack is +19 vs. AC. I roll a 10.) Does a 29 hit your AC?

Alard (Steve): Yeah, it does.

DM (me): Okay, the minotaur hits for 22 points of damage.

Using the active defense variant, the same attack might go something like this:

DM: The minotaur swings his greataxe at you, seeking to lop off your head. How do you want to defend against the attack?

Alard: I turn my shoulder into the blow to absorb the damage where my armored hide is toughest. (Steve rolls 1d20 and gets a 10, adding 16 for his armor defense.) How’s a 26 for armor defense?

DM: You turned too far, and the minotaur lands a blow between your shoulder blades, or whatever the warforged equivalent is. (I roll damage …)

In this example, the minotaur needs to roll a 7 or higher in standard D&D to hit Alard’s AC of 26, so it has a 70% chance of hitting Alard. In the active defense scenario, Alard needs to roll a 15 or higher to block the minotaur, giving him a 30% chance to block and the minotaur a 70% chance to hit. (Having attackers “take 11″ instead of “take 10″ keeps the probabilities the same on both sides of the mirror. If attackers “take 10,” the probabilities swing 5% in the players’ favor.)

But this system brings up alternative possibilities as well. Suppose the exchange went like this:

DM: The minotaur swings his greataxe …

Alard: I bring up Bryndlgore to block the incoming axe.

DM: Okay, let’s call that a Fortitude defense roll.

Alard: (Steve rolls 1d20 and gets 18, adding 15 for Alard’s Fortitude defense bonus.) How does a 33 grab you?

DM: There’s a loud clang and a shower of sparks as Bryndlgore stops the incoming axe cold.

In this instance, Steve takes a chance, since a monster’s attacks vs. AC tend to be +2 higher than their attacks against other defenses (exceptions exist, of course).

At some point Steve might recklessly decide to take an even bigger chance:

DM: The minotaur swings his greataxe …

Alard: I duck under the swing.

DM: Okay, give me a Reflex defense roll.

Alard: (Steve rolls 1d20 and gets 3, adding 13 for Alard’s Fortitude defense bonus.) Eh, no, 16.

DM: You duck straight into the blow, which deals you (I roll dice) 23 hp of damage.

Now, what if Steve wanted to say, “I just stand there and take it, willing myself to feel no pain”? Could Alard make a Will defense roll to resist damage? Since hit points are an abstraction that includes morale, determination, and other such qualities (insert obligatory Rocky Balboa analogy and why-warlords-can-heal discussion here), why not? A DM who feels that the PC’s chosen defense is particularly inappropriate against the relevant attack can always give the monster’s attack a +2 or +5 bonus, depending on just how wild the suggestion is. If the player can come up with sufficient storyline to support it, why not allow it? Even a suggestion as strange as using armor defense against a mental attack could be workable if the player suggests something like “my shield reflects bright light into the mind flayer’s sensitive eyes.”

I’ve only been thinking about this idea for a few hours, but so far, it really appeals to me. I think it has the potential to encourage better in-combat role-playing, and to make characters feel more active in the battle. If my players agree, I may even turn this thought experiment into a real experiment the next time we play. If so, I’ll let you know how it goes (and, of course, you’ll hear it on the Icosahedrophilia podcast).

15 Comments

  1. Honestly there are plenty of games out there (especially wargames) that use a similar mechanic where each opponent rolls off against each other. Immediately what comes to mind, at least if the PCs just used this, would be a more interactive combat experience.

    D&D suffers from the I Go You Go turn mechanic. They do all their actions and then sit out the remainder of the turn. At least with an active die roll for defense they are in the game, rather than being a static punching bag.

    Expect the old-timers to revolt in droves claiming that DnDNext destroyed D&D if something like this rears its head though.

  2. I really like active defenses (they were in Unearthed Arcana 3e) where players just roll the dice and I agree the way you describe your variant where they can narrate to pick which defense to roll can help make for some good descriptions. The only problem is if the PC can effectively choose which defense to use, why wouldn’t they pick their highest defense every time? This may or may not be a bad thing, but it will mean that monsters hit less often. I’m not sure the PCs need that much help on defense.

    Perhaps make changing the defense cost an action point or something?

    • Aoi, Allowing th PCs to choose the defense does run the risk of monotony in the sense you described. However, there are a couple of balancing factors. First, I’d demand a storyline reason why that defense is appropriate. If that “reason” sounds like just a lame excuse for using a high defense, I’d give the monster a +2, +5, or even +10 bonus. Alternately, I might rule that a miss against a questionable defense deals half damage instead of none. Second, if the monster’s attack is normally against AC, the player would give the monster a mechanical advantage if the chosen defense is lower than AC + 3. Third, I might be inclined to transmute AC into DR instead of a defense, but I need to think this through more.

  3. Some interesting things to be addressed.
    Do monsters score a crit when the player rolls a 1?
    How do you handle PC’s attacking PC’s? NPC’s attacking NPC’s?
    Simply using active defenses makes characters 2.5% harder to hit. (the average of a d20 is 10.5) If the player gets to choose the defense then this can get much greater.
    Optimizers will try to max one defense and use it all the time. With class, race, feats and items it’s easy to get one defense that’s higher than the others by five or more. If you push two defenses then they can probably cover most attacks with minor penalties, and it’s much easier than pushing four defenses. I see the big problem with inappropriate defense being the switch to and from Will. It can see less penalties switching between AC, Reflex and Fort.

    • Philo, I hadn’t really thought through the PC vs. PC or NPC vs. NPC question. That doesn’t come up often in my games, although I have had a few monsters that “mind control” PCs into attacking their allies. I need to think through those issues more carefully. My first impulse is to say that if a PC’s attack vs. another PC is unintentional, as in the case of a charm effect or something, the attacking PC is functionally a monster and takes 10 on the attack, while the defending PC uses active defense. If the PC vs. PC attack is intentional, then both PCs could roll dice and there is no static 10 to add anywhere. For NPCs attacking NPCs, if the attack is intentional, I’ll just narrate what happens. If it’s an NPC/monster attacking another NPC/monster under the control of a PC’s charm effect or something like that, I’d let the PC roll the d20 for the attacker and compare that to the target’s static defenses. The core principle would be that an attack initiated by a PC (even if carried out by a monster or an NPC) is 1d20 + bonuses, and an attack initiated by a monster (even if carried out by a PC “under the influence”) is 10 + modifiers vs. active defense roll. I need to test this, of course. It’s just a first draft.

      As for the to-hit percentages, I don’t think the arithmetic mean of a d20 (10.5) is really a meaningful measure here. Nobody ever rolls a 10.5 on a d20. Since only whole numbers are possible, the to-hit chances change in 5% increments. I’ve corrected the original post to reflect this.

      I agree with you both about optimizers and about the Will defense, and I think it’s up to the DM who moves toward active defenses to compensate for those factors by controlling the proliferation of magic items, policing the appropriateness of defense choices, and so on. To continue the example from the post, if Alard tried to use Will defense against the minotaur’s greataxe, I would probably say something like, “So you’re just going to let it hit you, and you’re going to try to think the damage away? Okay, you can do that, but the minotaur will get a +5 attack bonus since you’re not actively interfering with the attack, and a miss will do half damage.”

  4. I have switched to an active defense for all rolls a while back, even with characters attacking monsters. This method, honestly has added a new dimension to our gaming nites, it seems everyone now has gotten into what their character can do and what their imagination can come up with.

  5. I really like the idea of active defence.
    I like the idea of the players rolling all the time, keeps them engaged more. Don’t like the idea of choosing your defence, seems like metagaming to me and negates the importance of some classes non-AC targeting powers (ie Chaos Bolt).
    On PC vs PC there is no reason both couldn’t roll, adding their attack or defence bonus and comparing, the hit chance would work out the same.
    Critical hit mechanics need some thought, but could work.

  6. I really like the concept, but I fear it would add almost double the time to battles which, IMO, already take too long.

    I’d love to see you pursue the idea better and would love to hear it work in a podcast.

    If there were a way to do this quickly, I think gameplay would be more fun.

  7. I added “active defense” to Pathfinder. Originally, when I’d roll for the monster’s attacks against the character’s static AC and give the results, I’d look up and see their eyes start to glaze over, even when I added flavor text to the combat, to make it interesting. So, after reading up on it, I figured that adding active defense, the characters rolling to determine their own defense, that it engaged them more. NOW they’re looking at all the bonuses they can get from Feats, etc. to bolster their defense. It has really engage my players, and it hasn’t made the combat shorter (actually, I think has), but my players not bored, they’re ready with the dice to see how their characters will survive the combat. So, I applaud it!

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