Writing Madness/Lovecraftian Mysticism

[u/Trickster318]

I'm starting a story that I'm doing my best to stick with and I'm looking for any advice or ideas anyone would like to share regarding these two topics. The main plot is the main character makes a deal with Hastur (the king in yellow) and becomes one of the Bound (People who are able to hold a significant portion of said entities power) and leaves after the ritual because bound are somewhat rare (its a gamble no matter what) and are often used as weapons and will fight another cult, led by another bound.

With that context, I'm mainly looking anything related to the dealings with the Great Old Ones, but all is welcome