Scouting the Training Ground
The quest is located at the icon of Sidon, found just northeast of Zora's Domain. This quest is unlocked after completing the Relentless as a Waterfall Chapter 6 scenario. Completing the quest will unlock the Duel on Ploymus Mountain quest.
"The waterfall-climbing class is set to take place at Lulu Lake! Sidon is eager to give the spot a look-see, but there's a Lynel nearby on Ploymus Mountain, so he must take a stealthy approach..."
"Sidon returned to a hero's welcome. He confirmed that Lulu Lake would be a perfect spot for the workshop... after they hired a lightning wielder to defeat the Lynel, that is."
- Sidon: Bonus Combo