Dexion will to tell the Dragonborn that he can no longer read the Elder Scrolls as he has gone blind from reading the first due to a lack of preparation. He will then explain the Ritual of the Ancestor Moth that can be performed at Ancestor Glade, southeast of Falkreath.
If the Dragonborn has the alchemy perk Green Thumb, they can harvest two units of Canticle Bark. One with a value and weight of 0, the other with a weight of 0 and value of 350. However, if both of these Canticle Barks are put into any container and then removed, the one with 0 value and weight will disappear.