Accept The King in the Treeline
Find Father Orin by the small house and crates, with the quest marker over him. Open his dialogue and accept The King in the Treeline. Before attacking, confirm that the boss objective is visible in your active Quest panel.
The dialogue uses the wording End the Barbarian King before he swings twice. Follow the active objective and any failure message in your game; the wording alone is not a tested two-swing strategy. Begin with the opening quest route if ordinary enemy fights are still difficult.
Find the named boss
The Barbarian King is visible on the grassy area near Father Orin in the walkthrough. Read the enemy nameplate before using spells; fighting a different nearby target will not answer this boss objective.
Fight with the spells you have
Before attacking
Check your HP, mana, active quest and available spells. Plan a spell you can use while leaving room to move.
During the encounter
The Wind demonstration uses Gale White Bow from a distance while moving. Try keeping space to react, then use your own available spell sequence. This is a practical approach to test, not a guaranteed kill for every book.
If a spell is locked
The pictured Wind panel has Book Lv 11, with its Lv 20 spell still locked. Use your available attacks and work toward the next Book Level checkpoint if you need another spell.
Check the result
After the encounter, read the quest panel and follow its completion or turn-in instruction. Then inspect your rank title and Merit display. A title change is rank progress; it does not mean every other spell or awakening checkpoint is complete.
For another NPC-and-target route, use the Village Elder and Fox Mage quest. Keep the target name and active counter visible there too.
Something different in your game? Send a correction with the relevant panel.