The quest is unlocked after completing The Future of Hyrule scenario. Completing this quest unlocks the Terrako's Training challenge, as well as the Testing... Testing... One, Two... and Terrako, Empowered quests.
"You hope to revive Terrako, so work with everyone to collect parts that could do the job. With hard work and hope, you might just bring your little friend back to life."
"Welcome back, Terrako! The repairs have made your friend more powerful than ever, so it can fight alongside you as a faithful companion. What great news—more adventure with Terrako!"
- Repair Terrako