What can PCs find out about creatures using knowledge skills?

Question

I'm new to D&D and I'm a bit confused about using lore. I already saw Does D&D 5e have a rule for character knowledge about monsters? and know that a PC can use knowledge skills to learn about things, but I'm not sure what they can learn.

Let's say during or after a combat a player asks about the enemy creature, for example a goblin, and they want to use a knowledge skill for this. As the DM, I set a DC for the roll and if they succeed… what can I tell them about the enemy? Can I tell only goblin lore — origin, how they live, etc. — or can a DM even say its attributes such as AC, HP? Is there any way a player can even ask about enemies abilities or attributes? If an enemy monster has some special actions apart from melee/ranged attacks, is there any way for the players to find out by the rules when the DM must tell them?

Answer 1

You are the DM - it means whatever you want it mean.

Some people like to play the game with things like AC and hp a mystery and others prefer these things to be known to everyone. Both ways are 100% correct.

If you choose to play the first way then you are obliged as DM to make it clear in your description how strong the opponents are so the players' can make intelligent choices about when to engage and when to withdraw. Alternatively, if you put the numbers on the table then this is irrelevant.

Personally, I play with experienced gamers who have a pretty intimate knowledge of the rules and can usually pick from a brief description what they are up against. How do I reconcile the gap between what the player knows and what the character knows? Easy, if the player knows it the character knows it and vice-versa. How? Because the character grew up in a world with goblins and dragons so they know about goblins and dragons just like I grew up in a world with cars and Americans so I know about cars ( I don't understand Americans but that is due to general disinterest) :-)

Answer 2

Lore reveals should reflect character build and story

Lore check rules deliberately leave things very open to DM discretion, but hints about how this should work are scattered through the Player’s Handbook.

A little history

In the previous edition of D&D (4th Edition) what information could be gleaned from successful lore checks was codified, and any character who succeeded on the check would glean the same information.

While this made it easy for a new DM (like yourself) when I tried using the system, my players found this unsatisfactory. They would ask, as a member of their particular class, race, etc., wouldn’t they know some other kind of detail?

Backgrounds and Character Builds

Guidance on what knowledge characters have is now scattered though the character options section of the Player’s Handbook (Chapters 2, 3, and 4) as well as in other character build rules, e.g., The Sword Coast Adventurer’s Guide.

Regarding your example, characters with the Soldier background know “how to say alive on the battlefield” (Soldier background, PH p. 140) so they might know signficiant details about “enemies’ abilities or attributes” — especially if they had been involved in a military campaign against that particular enemy/creature type.

(Aside: Whether you as a DM reveal the exact AC or Hit Points is more a play-style issue. Some groups feel this meta-gaming breaks immersion, and prefer to use “in game” language for this, such as “The goblins are a little tougher than the kobolds you fought before.”)

On the other hand, if that creature has “special actions apart from melee/ranged attacks” that are never relevant to the battlefield, a different character might know more about these details. “A sage values knowledge highly—sometimes in its own right” (Sage background, PH p.138) so a character with this background could be more knowledgeable about the esoteric details about any topic.

Don’t let the dice tell you what to do

Sometimes a particular character (in your judgement, as DM) would definitely know a relevant detail. Reveal this information even on a bad lore check. For example, a cleric would recognize a depiction of his own deity.