You helped Hoz's monster-control crew defeat the monster forces in Hyrule Field, and now he has moved on to Fort Hateno.
Quest Location
This quest begins at -0440, -0585, 0027 after you complete the quest Bring Peace to Hyrule Field!.
How to Complete the Quest
After you help Hoz's monster-control crew defeat the monster forces in Hyrule Field, you can find Hoz if you go north from Dueling Peaks Stable then go east before the bridge. (If a blood moon occurs, Hoz's crew will not be at Fort Hateno; you will need to go back to Hyrule Field and help Hoz's crew defeat those monster forces again, then come back to Fort Hateno.)
When you find Hoz's crew near Fort Hateno, talk to Hoz, then follow him to the location of the attack, and help defeat the monsters. When they are all defeated, there will be a cutscene. Afterward, you can pick up all the monster parts and weapons and other items.
Quest Reward
Hoz gives you 100 rupees.