In The Legend of Zelda: Tears of the Kingdom, speak with Mastro at Snowfield Stable to obtain the Serenade to Mija side adventure.
For this quest, you’ll need to travel south along the road to just south of Nero Hill.
You’ll find a crater with some smoke coming out of it.
Jump inside and speak with Eustus who will task you with a new side adventure called The Hornist’s Dramatic Escape.
For this adventure, Eustus is unwilling to leave the hole without his wagon. You have 2 choices to accomplish this. To his left you’ll see some building supplies which you can use to construct a flying apparatus to lift his wagon out of the crater. Alternatively, you can stack the 3 crates on top of each other near the edge then use Ultrahands to lift the wagon out of the crater. Whenever you’re ready to take action, have Eustus hop in the cart to lift him out too! As a reward for getting him out, you’ll receive Courser Bee Honey x3.
Afterwards, return to Mastro at Snowfield Stable. When you speak with him, he’ll need you to construct a roof for the breezer. This one is easy peasy! Just slap a wooden board onto the roof of the breezer then tell him that you’ll take him.
Since there’s no horse attached, head to the stable and speak with Varke to grab a horse and have him equip it with a tow harness. Mount the horse then bring it to the Great Fairy on the hill nearby. As a reward, Mastro will give you a Silver Rupee!