Originally mentioned in The Whisperer in Darkness by H. P. Lovecraft in passing, many details have been filled out by subsequent authors (and The Call of Cthulhu RPG). A Brotherhood of the Yellow Sign also appear in The King In Yellow by Thom Ryng, although it is unclear if they are connected with the usual cult of this name.
Who are they?Edit
The Brothers of The Yellow Sign (also linked to the Cult of The Yellow Sign) are considered to worship Hastur in his aspect as The King In Yellow. The cult is led by a group of human immortals from the technologically and physically advanced realm of K'n-Yan (the cult probably originated in this subterranean land, though others trace it to the Serpent People of Valusia), though it's worth noting that these immortals worship other gods too.
What are their methods?Edit
The Brothers of The Yellow Sign are known as being a particularly brutal cult, even by other Outer Gods' and Great Old Ones' standards. In particular they are known to torture members of the Great Race of Yith and wage war against the Migo.
What are their beliefs?Edit
Unknown. Presumably the cult has leanings towards Hastur and The King In Yellow through their devotion to The Yellow Sign.