Particular sorts of alien entities are more likely to teach particular spells to worshipers.
From an Outer God – Call/ Dismiss Azathoth, Call/ Dismiss Shub-Niggurath, Call/ Dismiss Yog-Sothoth, Contact Nyarlathotep, Create Gate, Dread Curse of Azathoth, Powder of Ibn-Ghazi, Shrivelling, Summon/ Bind Dark Young, Summon/ Bind Hunting Horror, Summon/ Bind servitor of the Outer Gods, Voorish Sign
From an Elder God – Brew Space-Mead, Contact Nodens, Elder Sign, Summon/ Bind Nightgaunt.
From a Great Old One or via Servitor Race – Brew Space-Mead, Call/ Dismiss Cthugha, Call/ Dismiss Hastur, Call/ Dismiss Ithaqua, Call/ Dismiss Nyogtha, Contact Deep One, Contact Deity/ Cthulhu, Contact Deity/ Tsathoggua, Contact Deity/ Yig, Contact Ghoul, Call Mi-Go, Contact Star-Spawn of Cthulhu, Create Gate, Summon/ Bind Byakhee, Summon/ Bind Fire Vampire
From an Independent Race – Contact Chthonian, Contact Deep Ones, Contact Ghoul, Contact Mi-Go, Contact Sand-Dweller, Contact Star-Spawn of Cthulhu