Spirit-Studded Tome

The Spirit-Studded Tome is an item that can be found extremely rarely as one of the books in a Dungeon, appearing in 1 out of 150 worlds. Other than that, it can be crafted.

The tome has a unique effect when bound to any weapon that is not a tool (repeater, bow, sword, etc.). When bound with a weapon with a Bounding Table, it will permanently be bound to that weapon, buffing the weapon's rarity exponentially. If a boss is defeated using a weapon bounded with the tome, the boss has a 12.50% chance to drop a unique item.