Tell us what you know! INT checks & monsters in D&D 5e

Recently on twitter someone asked how DMs can determine how much a player character knows about any particular monster in 5e, since knowledge checks aren’t as granular as they were in previous editions. I sent him a link to the 3.5 SRD description for the Knowledge skill, which can be helpful, but I felt I could be more helpful than that. Let’s dive in to Monster Knowledge!!!

Fifth Edition Basics

As written, the rules for monster knowledge in 5e are a bit vague. The PHB details how to make Intelligence checks on pages 177-178. Similar to the sub-types of Knowledge skill checks in 3.5, 5e gives some guidance, but we have to extrapolate a bit. From the 5e SRD:

Arcana. Your Intelligence (Arcana) check measures your ability to recall lore about spells, magic items, eldritch symbols, magical traditions, the planes of existence, and the inhabitants of those planes.

History. Your Intelligence (History) check measures your ability to recall lore about historical events, legendary people, ancient kingdoms, past disputes, recent wars, and lost civilizations.

Nature. Your Intelligence (Nature) check measures your ability to recall lore about terrain, plants and animals, the weather, and natural cycles.

Religion. Your Intelligence (Religion) check measures your ability to recall lore about deities, rites and prayers, religious hierarchies, holy symbols, and the practices of secret cults.

I’ve left out Investigation, since you could only really use that outside of combat, and we’re looking for something to use in the heat of the moment.

Arcana use seems overly broad as read “the planes of existence, and the inhabitants of those planes.” That sounds like you can use Arcana to recall lore about anyone, anywhere! My gut tells me that they didn’t mean to include the Prime Material plane in this one, only outsiders from other planes, but that’s up to you as the DM. Arcana would seem to be your starting point, though. Use Arcana for: Aberrations, Celestials, Constructs, Elementals, Fey, Fiends, some Monstrosities (when magic was used to create them), and Undead that were created with magic.

History is, well, for historical events, but such lore might provide clues on how to defeat a monster. For example, the bard in your party might remember an epic poem about the time a monster called “The Land Shark” devastated a small village, and how a wandering group of adventurers finally managed to kill it, providing some insight when fighting a Bullette. Use History for any monster type, but only if you, as the DM, know of, or wish to add an historical event in the campaign world that would be relevant. Just because a player can try using this skill doesn’t mean you are obligated to provide an answer every time.

Nature, obviously, should provide players with knowledge about natural animals; bears, wolves, etc, not to mention plant-type creatures, or perhaps even elementals if no one in the party is good with Arcana. Use Nature for Beasts, Dragons, Elementals, Fey, Giants, Humanoids (from the Prime Material Plane), some Monstrosities (if they are naturally occurring), Oozes, and Plants.

Religion doesn’t really mention anything about creatures per se, but I don’t think it’s much of a stretch to allow players to make a religion check to see what they know about demons, devils, or good outsiders that serve deities. You might also allow religion checks to know about undead creatures, or aberrations, since it covers cults that might worship creatures from the Far Realms. Use Religion for Aberrations, Celestials, Elementals (as worshiped by cults), Fiends, and Undead.

meta-gaming-2Those four INT checks will cover you for the “how” to check, but that doesn’t really help you with the “what” or how hard it should be to know information about a creature. As the DM the simplest thing might be to use the default DC ranges and decide whether you think the creature the PCs are facing is commonly known by the populace of the world, or obscure. That will guide you to the appropriate DC. You could also give some thought about the info itself the PCs want to know. For example, if a PC just asks what they know about the monster they are fighting, a DC 5 check might reveal it is a goblin, since goblins are common. A DC 10 check might reveal the average “health” (in hit points) of a goblin, or how skilled they are with a sword, and a DC of 15 might reveal the goblin’s Nimble Escape ability. You might decide these DCs are too easy for your campaign, that’s up to you.

By comparison, the name, hit points, strength or abilities of an Invisible Stalker might be much harder to ascertain in the heat of battle. You can use Hit Dice and/or CR as a guide to how hard it may be, but again it depends on your campaign world. Maybe Invisible Stalkers are everywhere, and the subject of many stories told to each generation to frighten children into doing their chores.

Remember also that a failure doesn’t necessarily mean the PC knows nothing; it could mean they recall something erroneous! If you want to play it this way, you might want to roll for the PC.

If this isn’t enough guidance for you, we can look to past editions for some help.

3.5 Knowledge Skill

5th edition Dungeons & Dragons does a great job of streamlining and simplifying the game. It moves more quickly than previous editions at the cost of in-depth rules to guide DMs and PCs. By comparison, 3.5 had very specific rules for determining how much you could know about a monster.

Answering a question within your field of study has a DC of 10 (for really easy questions), 15 (for basic questions), or 20 to 30 (for really tough questions).

In many cases, you can use this skill to identify monsters and their special powers or vulnerabilities. In general, the DC of such a check equals 10 + the monster’s HD. A successful check allows you to remember a bit of useful information about that monster.

For every 5 points by which your check result exceeds the DC, you recall another piece of useful information.

It also delineated which sub-class of knowledge included which type or sub-type of monster, for example Knowledge; Arcana included constructs, dragons, and magical beasts. The challenge with this skill however, is that it could be nigh impossible to even know the name of the monster you were facing if its hit dice were particularly high. Some might argue that this is okay, that to know more about tougher monsters you needed to be more experienced, but doesn’t account for generalized knowledge people might have from stories, or studies done by sages and other adventurers that even a first level PC might have read.

If you want to make it challenging for your PCs to know what their facing in 5e, you wouldn’t go wrong using the 3.5 Knowledge skill rules.

Bring on the Lore!

Later in 3.5 the fourth Monster Manual came out, and included a section for each monster entry that included lore about the monster, and had a chart that showed various bits of info a character might know, and the DCs for each. This Lore approach was also use in the amazing Ecology articles in Dragon magazine. (Honestly, if you want to get more background info for some iconic D&D monsters, check out Dragon’s ecology articles from about 2005 until they stopped printing.)

The Monster Manual IV addressed the Knowledge skill checks in the PHB as being for knowing “specific creatures very well”, but opined that:

…there’s more to be said about creatures of general types. Consider the whisper demon as an example. It’s a 15 Hit Dice creature. That means that identifying it is a DC 25 check. This check will generally yield one bit of information, but since there are lowly 2 HD demons such as the dretch out there that share many of the demon and tanar’ri traits, it’s reasonable to give more information about it with the initial identification of the creature as a tanar’ri.

This monster manual was very generous, then, with what it decided players could know with their knowledge checks:

As a general rule of thumb, a DC 15 check or higher will reveal all of the base creature’s type and subtype traits as defined in the glossary. This often includes information about energy resistance or various immunities. For instance,
a DC 15 Knowledge (arcana) check reveals that dragons have high hit points (12-sided HD), all good saves, and have darkvision out to 60 feet and low-light vision. They are immune to magic sleep effects and paralysis effects. They eat, sleep, and breathe.

A good example of the Lore charts in Monster Manual IV is the entry for the Yuan-Ti. You can use this as an example to build your own Lore charts for creatures in your game, or as a guide on the fly.


New Options for 5e Characters

If you want to let your players have their characters specialize a bit more in knowledge of the creatures they may face, I’ve come up with a new Feat, and a new Background you might consider.

FEAT: Cryptid Study – You have spent long hours in study on a particular type of creature, and excel at recalling important details when encountering creatures of that type in the field. You may take Cryptid Sage more than once, choosing a new type each time, but your Intelligence cannot be increased above 20 in this way.

  • Increase your Intelligence by 1 to a maximum of 20.
  • Choose one of the following creature types. When you encounter a creature of this type, you immediately recall its common name, and gain Advantage on all Intelligence checks made to recall information about that creature. (Aberrations, Beasts, Celestials, Constructs, Dragons, Elementals, Fey, Fiends, Giants, Humanoids, Monstrosities, Oozes, Plants, Undead).
  • On the first round of combat you gain Advantage on one attack against a creature of your chosen type.

BACKGROUND: Cryptid Sage – From childhood you have always been obsessed with stories of creatures and monsters, the good, and the evil. You voraciously read every book you could find, and even studied with other learned researchers, or even tagged along with adventurers to make sketches and notes first hand. Now your years of experience and study have made you an expert in all things related to your chosen field.

Skill Proficiencies: Choose two from Arcana, History, Nature, or Religion.

Languages: Choose one language spoken by a creature from each of the two types you have studied.

Equipment: A journal, a quill, a bottle of ink, a small spy glass, a set of common clothes, and a pouch containing 10 gp.

Cryptid Specialty: Choose two from – Aberrations, Beasts, Celestials, Constructs, Dragons, Elementals, Fey, Fiends, Giants, Humanoids, Monstrosities, Oozes, Plants, Undead.

Feature: Field Expert – You are an expert on creatures from your two chosen creature type specialties. You can name any creature from those types on sight, and can usually remember one or two important facts about their ecology (how they live, reproduce, likely alignment, and other characteristics that might affect encounters with them). You also know where to find more in-depth information – how they might act in combat, their strengths and weaknesses – in libraries or from other learned sages. When observing such creatures in the field you gain Advantage on Insight rolls made to determine their mood or behavior when you are within 30′, or with your spyglass from 60′.

d8 Personality Trait

  1. I am intensely curious, especially where deadly monsters are concerned.
  2. At best I am indifferent to other people, but very excitable and passionate engaging with, or discussing, monsters and other races.
  3. I cannot pass up the opportunity to discover new information about other living things.
  4. I don’t like knowing less than others, especially where my studies are concerned. I frequently make things up to compensate.
  5. I am very protective of my family, friends, and community. I will defend them from the bad things in the world.
  6. I am the greatest expert in my field. Only my jealous peers would say otherwise.
  7. I prefer caution, and careful, quiet consideration of every encounter. Mistakes can be costly.
  8. The world is an incredible place, with so much to see and experience! I can’t sit still, there is adventure to be had!

d6 Ideal

  1. Knowledge. Good and Bad are arbitrary, but facts are immutable, and the ultimate pursuit. (Neutral)
  2. Mastery. I will not let the monsters of the world harm others, they will be controlled! (Lawful).
  3. Beauty. There is goodness in everything, you just have to find it. (Good)
  4. Destiny. The monstrous races of the world are superior in every way. They must, and will destroy us. (Chaotic)
  5. Power. It is possible to assimilate the best traits of the monsters in the dark, and become even more powerful! (Evil)
  6. Confidence. By understanding the creatures around me, I will come to understand myself and my place in the world. (Any)

d6 Bond

  1. I had a monstrous creature for a pet, but villagers killed it out of fear. I can’t let that happen again.
  2. My village was almost completely decimated by a pack of strange creatures. I will protect others from the same fate.
  3. I have been entrusted by my patron with the great task of humanely cataloguing all the wondrous creatures of the world!
  4. I have nightmares of an impending cataclysm wrought by monsters from the deep. It must be averted.
  5. I once received a telepathic message from something beautiful beyond our world, and I must find it to feel that mental euphoria again.
  6. I am being paid very well to bring back rare specimens, alive or dead, of some very dangerous creatures.

d6 Flaw

  1. I am easily distracted by the beauty of the creatures I encounter, even the dangerous ones.
  2. I do not trust the creatures I’ve studied, even if they are supposedly “good”. Even angels lie.
  3. I killed the sentient animal totem of a warrior tribe, who have sworn to skin me alive if any of them see me again.
  4. I am compelled to take a “trophy” from every creature I kill. I keep my trophies hidden from others.
  5. I’ll do anything to gain the renown of my peers in the study of cryptozoology.
  6. I want to understand how these monsters truly feel and will stop to ask them questions, even at inappropriate times.

That’s all I’ve got for now. I hope you will find something useful in this post. Please let me know what you think, including any feedback on the Feat or Background above; they are the first I’ve created for 5e! You can also find me on Twitter as @mjsoctober or on Google+ as +MichaelSchmidt.

Thanks for reading. Go roll those dice!



















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  1. Pingback: Identify Fiend or Foe – Gaming Ballistic

  2. Hey there just wanted fo let you know this background was a great inspiration for my monster hunter character i will be playing starting next month!

    I have added medicine to the choice of 2 skills and swapped a language for a herb kit due to his more hands on approach to research and collection of ‘samples’


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