Ilvir: Guardians of the Serpentine Ring (ritual)
from "Nubeth Chantry" in Thonahexus #10
location/adventure: a chantry of the Guild of Arcane Lore
This article also contains an Ilviran ritual, Guardians of the Serpentine Ring, and an alternate treatment of the ivashu, umbathri (Hârnic gargoyle).