Kill Cragbeast Queen in Natimbi. This is a raid boss. Loot Phosphorescent Bile.
In open world, she is only up between 12am and 2am in-game time (Approx. 5 day respawn timer once killed). You can also spawn her in an instance, where she’ll always be up.
Head to Uqua with a raid. You’ll need to loot Unlit Ornate Beacon (2-slot container). It can drop off of both Spectral Trushar Worshipper and Devastating Construct (confirmed), and possibly Vrex Barxt Qurat (unconfirmed).
Combine Phosphorescent Bile into Unlit Ornate Beacon (2-slot container) to create your