Exploring dungeons is dangerous business, especially if you can’t see where you are going. While Elves, Gnomes, Dwarves, and many other species have Darkvision, which allows them dim black-and-white sight in darkness, Humans and most other species don’t have this ability. Before starting underground,  have each of your players check their character sheets and understand if they have Darkvision.

With Darkvision, players underground will be able to navigate, attack, and defend themselves normally. Without Darkvision, everything becomes harder. The simple rule is everything a character does in darkness is at Disadvantage: Ability Checks, Attacking, and Saving Throws.

Adventurers without Darkvision will need another source of light. Make sure those players have torches or a lantern, oil, and a tinderbox written in their equipment. But unless you are a truly evil Game Master, don’t make players account for individual torches or quarts of oil.

One easy Game Master trick — nothing adds excitement to a run-of-the-mill encounter with yet another gang of Goblins like having to do it all in the dark! Imagine a Goblin spellcaster blowing out the party’s light source with a perfectly timed casting of Gust of Wind! Or a splashing tentacle dousing all the party’s torches! FUN!