Forgotten Feather
Drops from Forgotten Feather. Actually you don't need any special tool to get there , you just need to jump. Follow this path go to the end of it and just jump.
The 
Forgotten Feather is a toy that drops from a treasure chest on a floating island to the south-east of Keeper's Respite in Korthia, and is part of the Treasures of Korthia achievement.
Guide awaiting review
Reach the Ledge Entrance
Head to the ledge entrance at 63.91, 27.37 in Korthia, near the high point by the windrider above Keeper's Respite.
Glide or Jump to Island
From the jump point at 65.82, 28.16, you can either use a 
Goblin Glider Kit to glide across to the floating island, or simply jump — you will land with around 20% health remaining, so start the jump with full health.
Collect the Feather
Pick up the Forgotten Feather treasure, which appears as a small feather on the ground, at 69, 29.85 on the floating island.
Return to the Mainland
After looting the feather, run into the airstream on the island, which will carry you back across to the mainland automatically.
Tips
Arrive at the jump point with full health before leaping to the floating island, as the fall will reduce you to roughly 20% health.
