Found the usual way in the dark hole in umbra.
Give her 200 poison fungi and she will summon the plague for you.
You and your party will be teleported to the place where it spawns.
Any monster you encounter inside the Felucca dungeons will have a chance to be plagued. Plagued monsters will have a dark shade of green hue.
The rewards include custom artifacts and one color reward bundle.

• Gloves of the Leprechaun
• Kasa of the Raj-In
• Grizzley's Courage
• Dryad Green Bundle
• Bow of Weakening
• Titan Rings (Earrings)
• Lucky Sash (100 or 50 Luck)
• Tome of Lost Knowledge