An Ancient Formula

Journal
"Bokken from the trading post has hinted that he could brew a rare and incredibly powerful potion for the {baron/baroness/King/Queen}. However, he hasn't revealed what exactly he has in mind..."

"After all the trials and tribulations, Bokken has learned all he needs to know about the potion. All that's left is to wait for the results of his research!"

Walkthrough

 * Find the three books for Bokken: "Of Transmutations and Bodily Poisons", Part I, Part II, and Part III. See the item pages for locations.
 * Return the books to Bokken and wait until you have a throne room event where you receive a letter from Svetlana.
 * Travel to Oleg's Trading Post and talk to Bokken. He will ask you to dose a dog with his new potion. If you refuse any step from now on, the quest will be failed. The consequences of this are unknown.
 * Give the potion to the dog, then kill it, or untie the dog and go back to Bokken and lie to him about it.
 * Bokken will tell you to test the potion on wererats, which will unlock Wererat Lair but not reveal it. You can find the lair a ways to the west and slightly south.
 * You either attack them directly and test it on one of the mortally wounded ones, or trick them into drinking it. Regardless, there will be a combat.
 * Return to Bokken and tell him what happened. He will then drink another potion and attack you. Defeat him to knock him back to his senses. This completes the quest.