Bark up the Right Tree is a quest received by speaking to a powerful tree named Nericon that is guarding the way into the Crow's Nest district of Aleroth during the events of Divinity II: Flames of Vengeance.
When you approach the Champion Casca in Mardaneus Plaza near the city gates, one of his men (Bubo) goes headlong through the barricade towards Crow's Nest and gets struck down by conjured lightning. It seems that Nericon kills anyone who attempts to pass, human or undead. When approached, the tree speaks to you in a strange tongue that you don't understand, so you'll need to find a way to communicate with it. Behrlihn is appalled by your lack of linguistic skills, and suggests that you search a library for an ancient grammar book.
Do not venture too far past the tree yet, otherwise the same electrifying fate will be inflicted upon you.
If you have not done so yet, you'll need to complete the quest Seahorse Salad to gain access to the Forbidden Archive at the Prancing Seahorse on Lanilor Lane. That is where you'll find a lesson on the Elven Alphabet, located on top of a stack of books on the west side of the library.
Read the book and return to Nericon. Suggest that if he lets you pass, you'll put an end to the undead that plagues the city. This completes the quest and automatically assigns the follow-up quest Nericon's Wrath, which is tied in with Dead Rising and Clue IV of To Find a Wizard.
- 10560 exp, 2400 gold, and 3 skill books
- Three choices of: 5280 exp, 2400 gold, 1 charm, 1 formula, 5 gems, 1 jewelry (×2), 2 potions, or 5 potions [sic]