Coram Agh Tera

Cult of the Lionhead (or -headed) Spider is one of the religions in the Witchers series.

Glossary Entry
"Coram Agh Ter, called the Lionhead Spider, is a cruel deity who expects bloody sacrifices from his worshippers. The Cult of the Lionhead Spider is banned and there are but a few places in the world where its adherents can openly declare their faith. Temeria strives to eradicate belief in the Lionhead Spider, and the cultists are tried as murderers."

Mentions

 * near the end of Chapter I, Abigail may be revealed as a follower, cursing Geralt in the name of Coram Agh Ter
 * The cult has a lair in the Vizima Sewers

In the books
A Grain of Truth has a priestess of Coram Agh Ter lay the curse on Nivellen.