A Note on Darkvision

When I first started running a fifth-edition Dungeons & Dragons campaign, I took for granted that darkvision (and its predecessors and analogues, such as “infravision” in Advanced Dungeons & Dragons, “low-light vision” in Shadowrun and “night vision” in GURPS) improved a character’s or creature’s ability to see in both dim light and darkness. Then, while writing the first article for this blog, I inadvertently led myself astray by relying on the incomplete description of darkvision on pages 183–85 of the 5E Players’ Handbook, which seems to imply that it improves a character’s or creature’s ability to see only in total darkness. As both the PH chapter 2 race descriptions and the 5E Monster Manual introduction make clear, darkvision lets a character or creature see in dim light as if it were bright light (i.e., no penalty to Perception) and in darkness as if it were dim light (i.e., disadvantage on visual Perception checks, but not blinded). Thanks to Hemlock on the EN World forum for setting me straight.

Anytime a creature has darkvision, the natural implication is that it’s predominantly, if not exclusively, nocturnal or subterranean. In the case of monsters living aboveground, you can assume that they’ll prefer to attack at night, although they may sometimes move about during the day. However, unless there’s a reason to think of them as exclusively nocturnal (or if it serves the campaign to have the player characters stumble upon them while they’re sleeping), if a group of PCs encounters them, they’ll be awake and alert.

Click to reveal spoilers from The Lost Mine of Phandelver.

The Lost Mine of Phandelver begins with a goblin ambush: Two horses lie dead on the road, and while the PCs investigate, four goblins attack them from out of the woods. In all likelihood, this discovery takes place during the day. Goblins have darkvision. There’s not necessarily any contradiction here. While goblins may be more active at night and may prefer to fight at night, the travelers they enjoy waylaying move during the day. Therefore, if they want to carry out a successful ambush, it’s got to happen during the day.


In other words, darkvision doesn’t rule out the possibility of daylight activity. It simply tells us when and where a monster will fight, given the choice. If there’s some other situational factor that justifies a daylight encounter, of course it can happen in daylight. Otherwise, every aboveground D&D campaign would be a succession of discoveries of groups of snoozing monsters, which the PCs could either easily circumvent or slaughter in their sleep.

Why These Tactics?

Some basic premises I’ll be starting from:

  • Every creature wants, first and foremost, to survive. If it’s seriously wounded (by my definition, reduced to 40 percent of its maximum hit points or fewer—you may prefer a different threshold), it will try to flee. Exceptions are (a) fanatics or (b) intelligent beings who believe they’ll be hunted down and killed if they do flee.

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About This Blog

Any creature that has evolved to survive in a given environment instinctively knows how to make the best use of its particular adaptations.

That seems like a straightforward principle, doesn’t it? Yet monsters in Dungeons and Dragons campaigns often fail to follow it.

No doubt, that’s largely because many of us begin playing D&D when we’re teens (or even pre-teens) and don’t yet have much experience with how the world works. Or we come to D&D as adults with little or no background in the military, martial arts, evolutionary biology or even tactical simulation games, and so we don’t consider how relative strengths and weaknesses, the environment, and simple survival sense play into the way a creature fights, hunts or defends itself. Consequently, we think of combat as a situation in which two opponents swing/shoot/claw/bite at each other until one or the other goes down or runs away.

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