Euthanatos Sects

2nd Ed. core pg. 103 lists White Band, Consanguinity of Eternal Joy & Freedom Razor

1st Trad Book

New Groups in Euthanatos Revised

Pg. 94 Guide to the Traditions mentions the Pallottino family descended from the ancient Etruscans. Some are mages, some are mediums & hedge wizards. They are wealthy & focus on death-related magic. They are nominally members of the Euthanatos but the connection is weak. They keep to themselves.
Guide to the Traditions chapter 3: Order of the Black Willow is a barrabi group that takes its lead from Romanticism. Gothic horror, Victorian occultism led to spiritual corruption.

Bad Guy Groups

Lore of the Traditions pg. 92 makes sects simple for Mage 20: