Drachopedia

A Drachopedia is an item in Drachenjäger. It takes 1 inventory slot, and is primarily used by the Slugger Background. When reading a Drachopedia during combat, it expends the player's major action on their turn, and upon reading it, their next attack against a draconic creature gains an extra 1d6 for the player's choice of either the attack or damage roll.

With the Well Informed Feature in the Slugger Background, the player can read their Drachopedia as a bonus action, and gains improved extra rolls.

Acquiring a Drachopedia
Drachopedias can mostly be found and bought at libraries or bookstores for a decent price, though one of the equipment options for the Slugger Background supplies the player with a Drachopedia from the start.