My players often want to see if they know something about a monster or not, specially stuff like weaknesses and resistances. I have this idea that there should be somewhere in the MM or DMG explaining the proper way to do proceed, but I can't find it.

How do I know which is the best ability (skill) check for knowing about what a DMG monster can do and what it is weak against, and how do I calculate what DC is appropriate for such a check?

Please answer with RAW if possible. I already know I can adjudicate, which is what I always do, but I want to know if there is something in the rules that I have missed.

  • \$\begingroup\$ Well, you may be able to adjudicate but perhaps you aren't supposed to. Perhaps the omission is intentional and players are supposed to accumulate knowledge in-game? \$\endgroup\$ – Nagora Jun 19 '15 at 22:29

There are no, concrete RAW monster knowledge checks in 5e

The PHB, MM, and DMG do not mention anything like a monster knowledge check as existed in previous editions. Tied with that is the fact that monster types are not directly tied to skills. As such I can only offer guidelines based on my own experiences with 4e and 5e and what I have done as a GM.

Go with what makes sense for the creature/creature type.

Beasts for example might allow either the nature or survival skill to be applied to a knowledge check, arcana for any constructs or monsters from other planes, religion for demons, devils, and angels etc.

Apply the standard DC check ratio as laid out in all of the books and pdfs.

  • 10 Easy
  • 15 Medium
  • 20 Hard
  • 25 Very Hard

Passing the easy check lets the players know/guess the monster and its type. Medium Allows the players to know the types of attacks it will make (melee vs ranged and can it cast spells). Hard also lets the know resistances or immunities. Finally with a Very Hard DC met the players can look at the actual creature statblock. You can even restrict the Very Hard DC to only be given out to a player who is trained in the skill you are asking for.

That said, are monster knowledge checks required?

Its entirely possible for you as the DM to simply state whether or not a PC would know about a monster based on their backgrounds and experiences. You would need to discuss this option with players, but 5e's rules-lite narrative leanings would lend itself well to this so long as your players were on board with it.

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    \$\begingroup\$ I'd combine the rules for the standard DCs with additional information such as reducing the DC for famous or named monsters, or increasing the DC for obscure not-well-known monsters. \$\endgroup\$ – Sandwich Jun 19 '15 at 19:46

If you run a group focused on role-playing and stories, don't tell the players specific stats like armor class or DMG unless you see the need to. If your group is more combat-heavy, then stats would be more appropriate. No rule in the book really provides concrete guidelines to structuring knowledge checks.

I am aware that this question is asking about 5th edition. However, the 4th edition Monster Manual does include suggested checks for monster lore. Most of these lore checks include combat tactics, personality traits, flaws, but never direct stats. Perhaps they would give you an idea of how to structure your checks.

Example: (4th edition Monster Manual pg 138)

Goblin Lore: A character knows the following information with a successful Nature check.

DC 15 - Goblins are cowardly and tend to retreat or surrender when outmatched. They are fond of taking slaves and often become slaves themselves.

DC 20 - Goblins sleep, eat, and spend leisure time in shared living areas. Only a leader has private chambers. A goblin lair is stinking and soiled, though easily defensible and often riddled with simple traps designed to snare or kill intruders.

  • \$\begingroup\$ I am aware of the 4th edition rules, in fact that inspired me to ask this question for 5th edition. \$\endgroup\$ – arthexis Jun 21 '15 at 11:43
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    \$\begingroup\$ I feel that they are similar enough to be interchangeable. \$\endgroup\$ – user23475 Jun 21 '15 at 14:03

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