This hood can be bought from the Sea Scholar for 500 Gold after the Philosophical Pursuit quest is completed. Wearing the whole set (4 pieces) will gives 20 max health and sprinting will use less stamina.
Source[]
Sea Scholar Grandmaster Set[]
- Sea Scholar's Grandmaster Hood
- Sea Scholar's Grandmaster Robes
- Sea Scholar's Grandmaster Gloves
- Sea Scholar's Grandmaster Boots