Learning Vellan is part of the implied "starter quest" path of Book of Travels, but due to the intentional nature the game, it is both potentially missable and entirely optional.
Skip to step 4 if you are only seeking this specific achievement.The "starter quest" path can provide multiple achievements:1. During most new-character spawn points, you'll be guided by nearby NPCs to a teahouse which you can get optionally healed at for the
Reached Safety achievement.
2. The workers there will guide you to
Bat Saha island to find the
Dandelions Temple. Both of these locations are achievements.
3. Speaking with the guardians at the Dandelion Temple will guide you to the Deeplander, usually found in their cave on the western side of Bat Saha.
4. The Deeplander guides you to the robed teacher in the upper/northern part of the city itself. You must "Rest" (sit) down before them to trigger their dialogue. Afterwards, they provide the skill card for Vellan. You must use the item in your Inventory, then go into your Skill Book and "Learn" (equip) it.
After this is complete, there is no direct story arc to follow. However, the
Singer and Kasa Incident questlines as well as their connected
Vastila and Nightbathers arcs contain most the lore revolving around Chapter Zero's reason for Kasa being closed.