This mob spawns at -99,-134,-55.25 during the Anniversary period.
Findable (via Ctrl-F): Yes
You say, 'Hail, Tyla Filinav'
Tyla Filinav says 'Have you come to help me in my collection _____? There are quite a few items on my list and I'm worried about my chances to find them all. Would you be [interested] in helping me find them all?'
She starts the 8th Anniversary Scavenger Hunt task, with Lunar Fungus as a reward.