You can accept this quest from Looker in Nuvema Town after defeating the Unova Pokémon League. You can then begin locating and defeating the six sages across Unova, in any order.
–Surf HM required for sage Giallo and sage Rood
–Waterfall HM required for sage Giallo
–Strength HM required for sage Gorm
Gorm
Dreamyard ruins
Gorm can be found in the Dreamyard Ruins east of Striaton City.
Use Strength on the boulder south of the Dreamyard entrance, then continue south past the stairs and follow the path east to find the sage.
Ryoku
Relic Castle
Ryoku is located at the bottom floor of Relic Castle, within the Desert Resort. You can access it by flying to Nimbasa and going South or by flying to Castelia and travelling North
Zinzolin
Driftveil Cold Storage
Zinzolin is in Driftveil City’s Cold Storage.
Make your way to the back of the Cold Storage and walk into the open container, where the sage is hiding.
Bronius
Chargestone Cave
On Chargestone Cave B2F there is sage Bronius. Enter the cave from Mistralton City to travel the shortest route to him. He is near the magma stone location.
Giallo
Route U14
Giallo is on the upper cliffs of west U14. Surf north across the small lake near the route’s west entrance and climb the Waterfall with the corresponding HM to find the sage waiting at the top.
Rood
Route U18
To reach U18, surf west across the water in the center of U1, continue to follow the path west and pass through the U17 gate and keep surfing.
Cross over the mountain, then walk south to find Rood on the beach.
reward:
When the last sage is defeated, the quest is complete. In addition to trainer experience and money, completing this quest will reward you with the Unova Fishing Rod. You can also claim a Larvesta egg from Jonathan located in the house on U18 (needs an empty space on your team).