The Imp of Sodh says:
Deep in the Ulfenreach Mountains of The Onrothy lies Marwolaeth, the hidden stronghold of the Gareth Coil.
The Gareth Coil is an assassin cult devoted to the veneration of the fifth Faynarch commonly known as The Death Angel.
The Veneration of Grandmother Death
The lower tiers of the Coil believe they are merely assassins for hire, and they are not wrong.
The higher tiers are taught the Dham-Zehir (“Houses of Venom”)… the profane arts of bringing death into the world. To them, it is an unholy act of veneration that brings power to the practitioner.
The nine Guild masters meet in Marwolaeth five times a year to venerate The Death Angel through their leader, who is known only as Grandmother Death.
Grandmother Death is almost never seen by anyone except those guild masters; she rarely leaves her Chambers of Delight other than to issue orders during times of council or to teach the Dham-Zehir.
The tithe they pay manifests as blood dripping from her hands and feet, for their deeds and their path are drenched.
Her true name vanished from record decades ago. None know how old she truly is.
It is said that she feeds upon the murders committed by her guild masters and those who serve under them. She seeks apotheosis as the goddess of death in Fayn, and she will probably achieve it.
Grandmother Death presides over the Coil by allowing The Death Angel to manifest through her in order to instruct her guild masters on who should die next and how.
Marwolaeth itself is designed as a disorientating labyrinth. It is filled with cold stone vaults and guarded by hidden pits and razor-thin trip wires. In the shadows dwell silent sentries who will slay the intruder before he reaches the grand halls deep within.
That deepest sanctum is lit by brass braziers burning cold embers and floor stones worn smooth by centuries of sandals. At the dead center lies the Chambers of Delight… where Grandmother Death resides among rare poisons and morbid relics.