From Guild Wars 2 Wiki
Aurillium Capsules are used to acquire Wyvern's Liquid Fire for the Astralaria III: The Mechanism collection.“
Allows the collection of Wyvern Liquid Fire.
— In-game description
- If you have the Aurillium Capsule in your inventory and are struck by the Legendary Matriarch Wyvern's Fire Breath, you will receive Wyvern's Liquid Fire.