Joshun Felden tells you, "If you'd like to vastly improve your skill in Armor Tinkering, bring me a blank augmentation gem."
Joshun Felden tells you, "If you don't already have one of those, go talk to Fiun Rehlyun on the Halaetan Islands."
You give Joshun Felden Blank Augmentation Gem.
Joshun Felden tells you, "When you use this gem, your skill at Armor Tinkering will become a bit more... specialized."
Joshun Felden tells you, "But make sure you read the gem's inscription before you use it."
Joshun Felden gives you Jibril's Essence.