Spoiler warning: Quest and/or game spoiling details follow.

Obtainable in the Tomes of Knowledge Quest. You need to hand these books in to NPC Cael to unlock trading abilities with Farmine NPC's and other rewards. You can only give one Tome of Knowledge to him every 20 hours in real time.

Rewards for handing the tomes into NPC Cael:

• 1st Tome: Dragon Tapestry
  Allows you to buy Dragon Tapestries from NPC Pompan for 80 gp each.
• 2nd Tome: Minotaur Backpack
  Allows you to buy Minotaur Backpacks from NPC Pompan for 200 gp each and sell him lizard flags.
• 3rd Tome: Lizard Weapon Rack
  Allows you to buy Lizard Weapon Rack from NPC Esrik for 500 gp each.
• 4th Tome: Rice Balls
  Allows you to trade a Bunch of Ripe Rice for 10 Rice Balls with NPC Swolt. This can be repeated as often as you like, as long as you have a Bunch of Ripe Rice to give to Swolt.
• 5th Tome: Dragon Backpack
  Allows you to buy Dragon Backpacks from NPC Pompan for 200 gp each.
• 6th Tome: War Drum & Didgeridoo
  Allows you to buy War Drums (for 1000 gp each) and Didgeridoo (for 5000 gp each) from NPC Cael.

You need to have finished The New Frontier Quest in order to hand in the rest of the tomes

• 7th Tome: Snake Head Teleport
  Handing in 7 Tomes you will allow you to use the snake teleport at the peak of the mountain, inside of which Farmine is located. It takes you to the teleporter in northern Zao, south of the Dragonblaze Peaks which is the teleporter to Muggy Plains. The snake head teleport is a one-way teleport only!
• 8th Tome: Corruption Holes
  Allows you to enter a hole in the north-eastern end of Zao, where you can find many Lizard Chosen as well as 4 Ghastly Dragon.
• 9th Tome: Lizard Weapons
  Allows you to sell Zaoan Helmet, Zaoan Armor, Zaoan Legs, Zaoan Shoes, Drakinata, Sais, Zaoan Sword, Drachaku, Twin Hooks, Zaoan Halberd and Wailing Widow's Necklace to NPC Esrik.
• 10th Tome: Zao Palace
  Allows you to enter the Zao Palace. It is situated deep underground, below the mountain base of the Lizards. You will find Ghastly Dragons there, but before you get to them you will have to fight your way through hordes of Draken Warmasters.
• 11th Tome: Dragon Statue
  Allows you to buy a Dragon Statue from NPC Cael after you bring him a Red Lantern.
• 12th Tome: Dragon Throne
  NPC Cael will now make a Dragon Throne for you after you bring him a Red Piece of Cloth. There is a time limit on the Dragon Throne and Cael will only make them once per month for you!
• More than 12 Tomes: If, by any chance, you are able to get more than 12 Tomes, you can still hand them in to NPC Cael. He will reward you with 5000 experience points for each extra tome you give to him, but still only one is allowed every 20 hours in real time.

Spoiler ends here.