Fly in the Ointment

Fly in the Ointment is a Blade Quest in Xenoblade Chronicles 2. It can be received from Celliara by resting at in Theosoir, Kingdom of Tantal, after unlocking Dahlia's third Key Affinity reward,  and provided Nia, Tora, Mòrag, Zeke, Pyra and Dahlia are in the party. Completing it will unlock the first level of Dahlia's Icecraft.

Quest objectives

 * Gather Information about Kastina at Theosoir, Tantal.
 * Celesmia must be spoken to.
 * Look for Kastina, who was said to have gone towards the forest behind Old Gelgemos Gate, Tantal.
 * Investigate the snow mounds in the forest behind Old Gelgemos Gate, Tantal.
 * Checking the westmost snow mound progresses the quest.
 * Make an offering to the in the forest behind Old Gelgemos Gate, Tantal.
 * Threatening him requires clearing an Ice Mastery level 9 and Focus level 3 Field Skill check.
 * Go to Pillar City Ruins, Tantal.
 * Requires clearing a Fire Mastery level 3 and Focus level 5 Field Skill check.
 * Defeat all Sarta Garlus (4) at Pillar City Ruins, Tantal.
 * Report to Celliara at Anastatia's, Tantal.

Results
"Kastina is returned safely to her mother, and Dahlia is delighted with a gift of Moondrop flowers."