In Hyrule Warriors: Age of Calamity, There are four secret unlockable playable characters, and Terrako, Guardian of Time is one of the hardest to obtain.
Terrako the tiny guardian came from the future to save Zelda, and in order to get him in your roster of characters, you will have to fix him because he got broken in a fight against the calamity.
Once you have completed the main story of the game, then the Terrako quest will be available.
How To Unlock Terrako In Hyrule Warriors: Age of Calamity
You will need 50 Terrako components to revive the little robot which you can collect by working on the side quests.
The Quest is not much hard in terms of difficulty, but in order to complete it, you will have to do a lot of hard work.
You will need to complete all types of special Terrako challenges which are scattered around the map and also to complete the late-game side quests that will give you Terrako components as well.
After you collect all the Terrako parts by completing all side missions and challenges, the cutscene will begin featuring Terrako coming back to life.
Then Terrako will become available as one of the playable characters in the game, he has some unique weapons and abilities.
You will have to do a lot of grinding in order to get him, but your efforts will definitely pay off because it is quite fun to play with him.