Book of Sho'Gal
The Book of Sho’Gal (both copies you have are translations) contains various descriptions of the horror that is the outer god Sho’Gal. Sho’Gal is the god of ordered destruction, the remaker, the shaper of worlds to come. When she is loosed upon the Earth the end of days has come. She seeks to devour the world and create a cesspool of creation from the leavings.
Those who help her are promised a place of power in the new world. In the books, you have found descriptions of the spell that will summon her and have deduced how it works. You know that the spell requires blood of the kin of the chosen of Sho’Gal, the summoner who is casting the spell. You have deduced that a place of power is required for the spell to be successful as well as the correct lunar cycle, a new moon.
The places of power that the book mentions prominently is the Altar of Tears in Cairo (translator seemed to deduce this). The Circle of Stone in Alfholm and the Stair of Gods in Caroghta. The latter two you do not currently know the whereabouts of.
Both Hieronymous and Marjorie have read this book