Searching Eventide Island
The quest is unlocked after completing The Future of Hyrule scenario.
"It's possible that Eventide Island, so far out in the sea, might have some parts for repairing Terrako. A search party is going to head there, so prepare them for this difficult trip."
"The search party had a difficult task combing through Eventide Island, given the island's scarce resources. But with great resolve, the party found many parts that might revive Terrako!"