u/Chrisfiftytwo

Hi. I have an idea for a magic item that I want to give to my party that rewards them for Studying the monsters they come across and maybe even taking some actual notes etc on them.

If they aquire the book it would come with some vague instructions inscribed on the inside of the cover and the pages blank. The inscription would be something along the lines of "Monsters don't play by our rules or morals so we have to find ways to even the odds. Know that knowledge is power and use these pages to fight back."

The ideas is that if the player(s) take some time after a day of fighting to Study the book they will be able to put information about the beasts and monsters they have met onto the pages and gain benefits from it.

This is where I need the help as I am not sure how to do that mechanically without it becoming to strong.

One idea was that they would be able to use the book the next time they meet a monster of the same type that they had previously entered. They would use a bonus action (or action?) to infer something about the current one from its Statblock.

Another was that if they entered enough information (fight X amount of that monster) that they would get a permanent bonus against that type of monster. Like +1 AC due to knowing how they attack or +1 damage since they know their weakspots.

It was under this idea I wanted to potentially reward their own note taking. If they spent the time and actually wrote stuff down about the monster like the AC of a previous one they could use the book in the fight to check if the AC is higher or lower. Could reveal other kind of stuff as well if they paid enough attention during the fights and wrote them down.

The part I like the most myself is using their own notes as part of the books power but want it to give something on top of that for the cases where they don't have the specific details but did spend the time during camp to Study the book.

Any ideas on which direction I should go or other cool ideas on this theme?