Robbie's Research
Requirements
After showing Purah a picture of herself for the Locked Mementos Main Quest, talk to her again to get this quest.
Walkthrough
Set this quest as the objective marker to be guided to the Akkala Ancient Tech Lab.
When you get there, Robbie will want to see your scars. Remove all your armor so he can see them.
He'll then set you to get the blue flame, similar to the Hateno lab. Unlike the Hateno lab, the path back is full of monsters. While you can paraglide over to the area with the flame, it may be worth it to walk over there following the unlit lantern trail and clearing your route before heading back with the flame.
Once the furnace is lit, this will unlock the teleport spot. Go inside and talk to Robbie to complete the quest and get 3 Ancient Arrows.
In addition, you can now buy ancient gear, including the ancient armor set, from Cherry, the statue right in the middle.