Five Great Mothers
From The Heretic Knowledge Vault
Apparently, a group of figures in the trolls' religious system. We don't really know anything about them, except that they're invoked when a group of trolls starts swearing (quite understandably) at the sudden appearance of Ianilis.
There has been speculation that the Five Great Mothers might somehow be connected to the Paedagogusi, who are known to have interacted with the trolls. Facts are lacking at this stage of proceedings.