A major gripe that many GMs have about Dungeons & Dragons Fifth Edition is that the vision system in 5e is frustrating. It feels like just about every race has Darkvision or can cast a cantrip that allows them to see - so what's the point? When you're juggling NPCs, campaign notes, villains, and everything else, Darkvision can feel like just one more thing to keep track of and for little benefit.
Back in D&D 2e, there was a huge range of vision abilities based on a character's race. These included variants to how far creatures could see in the dark and different types of vision such as black and white or even infrared. However, this complexity was dropped starting with 3rd Edition in favor of simplicity. Now with 5e and how over-powered PCs often feel anyway, should we just ditch vision altogether and assume every character can see in the dark?
Impact on Rules
The biggest argument I can think of for keeping track of Darkvision is the relative significance it can have on the game. Adventurers who lack darkvision and are making an attack against a creature they cannot see have disadvantage on the attack. Disadvantage typically equates to a -5 modifier for rolls, or a 25% drop in the likelihood of PCs making their attack rolls. That's a massive change in probability and one that I personally believe is too significant to discount. And it's not just attack rolls that are affected by not being able to see in the dark. Any ability check or saving throw that relies on sight - which is a lot of them - would also gain disadvantage. However, whether or not an adventurer has disadvantage is just one consideration for how wandering around in the dark can affect game play.
If you're playing a survival or horror campaign, then Darkvision - and which characters lack it - can be a super useful tool for the GM to utilize in many situations. If the players are traveling through a cave blind and have no light source - or a limited one - lean on that lack of vision. Describe the smell of moldering animal hides, the sound of dripping water, and feel of the cool, damp rock walls. Engaging those senses while omitting visual sense is such an effective way to ramp up the sense of terror in your players.
Additionally, don't forget the limitations of Darkvision. Players may be able to see, but they can't see color and they can't see indefinitely down that dark tunnel. Is that sticky liquid blood or something else? Is that powder on the ground ash or bonemeal? Find ways to utilize Darkvision and its limitations to tap into your players' fear of the unknown. But how do you keep track of who can see and who can't?
Sticky Note Tracking
I keep a sticky note on my GM Screen with notes about which of my players have Darkvision and which ones don't. This works well for me but maybe you need to do something else that will work better. Experiment and see what works.
Once you do know, the way I manage Darkvision is I describe what the lowest common denominator can detect. For instance, if two members of the party don't have Darkvision, I describe what they can sense first. Then, I will use text or Facebook messenger to quickly describe what those characters who do have Darkvision can see. Or, if we're playing in person, I might take the Darkvision players to a separate room to describe to them what they see. This can be time consuming so I use it only in crucial moments where I want to amp up the tension, but it really helps to capture the fear of the unknown for those characters who are blind.
If, after reading all of this, you still feel like Darkvision is boring or a waste of time, I hear you. In this case, you'll want to just scrap Darkvision and assume everyone can see the same things. Or, if you want to get more creative, you can come up with more unique vision traits for your game. Take a look at those 2nd Edition rules if you can find a copy. Or make up your own.
Reddit user FlyingFoxPhilosopher came up with some great suggestions in this Reddit post here which I'll paraphrase below:
Elves gain advantage on hearing based checks.
Dwarves have a limited range 30 ft. tremor sense when on natural earth.
Orcs gain keen smelling.
Gnomes have unlimited instant use of detect magic.
Dragonborn have thermal vision.
In a game system that is commonly criticized for its overpowered PCs, Darkvision is an often overlooked and ignored mechanic that can create tension and help level the playing field in combat mechanically. How do you treat Darkvision in your game? Do you have unique homebrew adaptions of it in your game? Let us know in the comments below!