Source noun – A person who supplies information. Informant is a synonym for source in reference topic. You can use "Informant" instead a noun "Source", if it concerns topics such as beginning. popular alternative
The books become filled with his comments in the margins, mad sketches, attempts to find numerical codes in the passages, his conversations with a dead informant, and mirrored or backwards text that is subtly different from the source.
Also, according to the Mysterious Informant in the Prologue, Cyric - the patron God of all the Psychos For Hire - is apparently also dead, and their powers are being provided by another source probably Jergal.
Compare with the Mysterious Informant (an anonymous Deep Throat-like source who appears to give the protagonists some cryptic, fragmentary information before disappearing) and the Knowledge Broker (a source with a network of further information sources supplying all the information needed).