The power of invisibility would be incredibly useful to have in real life, yet it's par for the course in Dungeons & Dragons, as it's fairly easy to fade from view. There are a number of D&D spells and magic items that grant invisibility, while many creatures from the monster races can do so naturally. A D&D party will eventually come across an invisible foe, but there are effective methods for dealing with them using regular items and low-level spells.
The ability to turn invisible is incredibly useful to a D&D party, as it makes it easy for rogues to scout ahead, and for spellcasters to hide from enemy fire until they are ready to act. A Ring of Invisibility is especially prized among low-level parties, especially if it doesn't have Sauron looking for it, and the party members will fight over who is most suitable to use it in battle. The power of invisibility isn't a sure thing, as there are creatures that can detect people through other means, so players cannot rely on it in every situation.
The invisible foes in D&D should beware, as there is a dedicated anti-invisibility spell in the game, in the form of the 2nd-level D&D Divination school see invisibility spell. The problem with see invisibility is that it's so situational that the caster likely won't take it as one of their slots, especially in a game like D&D 5e, where casters have such limited range among their spell slots. There are other methods for unveiling invisible creatures in D&D that don't require a 2nd-level spell slot, but can still be effective as revealing an enemy's location.
How The Invisible Condition Works In Dungeons & Dragons
According to the Player's Handbook, a creature who is invisible is classed as being heavily obscured for the purposes of hiding. They cannot be seen, though they can still be heard, and creatures with a powerful sense of smell can still track them. In combat, an attack against an invisible creature has disadvantage, while the invisible creature has advantage on its own attack rolls.
The easiest way to become invisible is through the use of D&D's invisibility spell from the Illusion school. The invisibility spell description mentions that the player's gear is also considered invisible while in contact with them for the duration of the spell. If the invisible player attacks or casts a spell, then the effect of invisibility ends. The 4th level greater invisibility spell functions for a minute (10 rounds) and its effect doesn't break when the recipient attacks or casts a spell. In both cases, the spell has a concentration component, so harming the caster can potentially cause them to break the effects of the spell.
D&D's Create Or Destroy Water Spell Has Multiple Anti-Invisible Uses
The create or destroy water spell is great for campaigns with a survival element, such as in Dungeons & Dragons' Indiana Jones-esque adventure, Tomb of Annihilation and its jungles, as it means the party will always have access to drinkable water. It's also an incredibly useful spell for dealing with invisible opponents. The Create Water effect of create or destroy water can be used to create rain within a 30ft cube, which is quite a big radius for a 1st level spell.
A D&D player could argue that they would see an invisible creature's body being hit by raindrops, prompting at least a Perception or Investigation check to see their location. Once the spell ends, the floor in the 30ft square will be wet, so the players should be able to see the creature's footsteps in the water, assuming it tries to move close. This can be useful when cast on an area centered on the caster, as they will spot the enemy when they approach.
D&D Invisible Enemy Tips - Bring Flour Or Ball Bearings/Caltrops
D&D has some mundane items with a lot of uses. Not all online or offline D&D groups will have access to the spells necessary for uncovering invisible foes. Luckily, there are some commonly available items that can reveal where an invisible enemy is hiding. One of the cheapest and most effective options is flour, which should be available in most D&D towns. A container of flour should only cost a few copper pieces (if that), and its value as an invisibility detector cannot be understated. Throwing a container of flour on the battlefield will either reveal the position of the invisible enemy or will leave a patch that will reveal their footsteps if they try to walk through it. Watching an invisible enemy's footprints will give the player an idea of their current position.
There are some D&D rogue builds centered on item use and these are useful for dealing with invisible foes. Players with a little more cash could also use ball bearings or caltrops as an invisibility detector. These both cost a gold piece each, and they have different benefits. A bag of ball bearings can be spread over a 10ft space, providing a wider range of coverage and potentially knocking an enemy prone on a failed Dexterity save, revealing their position. The caltrops only cover a 5ft square, but they deal a point of piercing damage and reduce the enemy's movement speed by 10ft. In both cases, the enemy can move at half their speed to ignore the detrimental effects of the ball bearings or caltrops, but it's going to be a hard sell for the DM if they want to claim that the enemy doesn't disturb the items while moving and revealing their position, especially the ball bearings, as there are supposed to be 1000 of them in each pack.
Faerie Fire Can Outline Invisible Creatures In Dungeons & Dragons
The Dungeons & Dragons drow elves have anti-invisibility measures in place, thanks to their ability to cast faerie fire when they hit 3rd level. The faerie fire spell forces everything within a 20ft cube to make a Dexterity save, with objects naturally failing the save. Those who fail are outlined in colorful light and they lose the benefit of being invisible. D&D's Principal Rules Designer Jeremy Crawford confirmed on his Twitter page that the attacker also gains advantage on attacks made against the invisible creature. The faerie fire spell is useful in most combat encounters, and every Dungeons & Dragons group should have one caster with it prepped, as it's a great measure for dealing with invisible creatures.
Source: Jeremy Crawford/Twitter