How to reward player characters that take the time to research and read books, etc. about creatures or lore? [closed]

Question

For example, let's say a PC acquired a book about ghouls and took the time to thoroughly read through it. What are some ways to reward that player for taking the time in-game to do this?

Some things I've thought up myself (though I'm not sure if these would be 'balanced'):

• Giving the PC in question a +x amount of bonus to their attack when trying to hit that certain creature (or granting the PC permanent advantage when trying to hit it) because the PC has read about some of the creature's weak spots during his reasearch.
• Revealing 1 or more stats about the creature depending on the book and how much time they spend researching the topic. (By "revealing a stat" I don't necessarily mean giving the player knowledge of an actual stat, like its Intelligence modifier or something but rather saying something/hinting along the lines of "You've discovered that ghouls more than not tend to be driven by their hunger rather than their intelligence when it comes to making decisions.")
• Telling the PC about some of the creature's habits. Continuing the example of ghouls, this could be something like "Most sources seem to agree that ghouls rarely venture alone, on the contrary they tend to create groups or packs." or "Ghouls usually use their claws to paralyze their target before digging their fangs into it, assuring they can devour at their heart's content without the target struggling or escaping."

Other ideas, thoughts or comments are most certainly welcome.

Answer 1

The best way to reward a player that makes his character do something in-character is to give them "Inspiration". Inspiration is a mechanical reward for playing the way the Dungeon Master appreciates.

I'll quote from the Player's Basic Rules book:

Inspiration

Inspiration is a rule the Dungeon Master can use to reward you for playing your character in a way that’s true to his or her personality traits, ideal, bond, and flaw. By using inspiration, you can draw on your personality trait of compassion for the downtrodden to give you an edge in negotiating with the Beggar Prince. Or inspiration can let you call on your bond to the defense of your home village to push past the effect of a spell that has been laid on you.

Gaining Inspiration

Your DM can choose to give you inspiration for a variety of reasons. Typically, DMs award it when you play out your personality traits, give in to the drawbacks presented by a flaw or bond, and otherwise portray your character in a compelling way. Your DM will tell you how you can earn inspiration in the game. You either have inspiration or you don’t—you can’t stockpile multiple “inspirations” for later use.

Using Inspiration

If you have inspiration, you can expend it when you make an attack roll, saving throw, or ability check. Spending your inspiration gives you advantage on that roll. Additionally, if you have inspiration, you can reward another player for good roleplaying, clever thinking, or simply doing something exciting in the game. When another player character does something that really contributes to the story in a fun and interesting way, you can give up your inspiration to give that character inspiration.

Answer 2

Encounters that turn on specialized knowledge

Write an encounter that only the character with specialized knowledge can do easily. Some niche piece of information that allows them to recognize something particular about a ghoul being faced or a ghoul's den.

Example

Foo, the sage, knows about an esoteric subspecies of ghoul

The character, Foo, has read extensively about ghouls. He notices the telltale drag marks at entrance that resemble a poor attempt at sweeping and the relatively flat stone floor chosen for a lair. Indicate that this is some audiophilic ghoul den and tell them that they're unusually sensitive to voices.

Encounter solution using the knowledge

Set up the encounter such that if they can use only hand signals and no vocalizations, they can retrieve or get past the challenge without combat. The specialized knowledge is an alternative way to defeat the encounter. The reward is whatever exp and treasure the encounter would yield.

Allow the player to further interrogate the character's knowledge by asking questions. e.g. The player could ask "Does Foo know if they respond to footsteps?", and the answer could be "Foo seems to recall that these ghouls are known to ignore noises that don't come out of a mouth."