Seeing as how our very first arc on The Rolled Standard was Call of Cthulhu, as well as it being the only game we have ever revisited (besides Mörk Borg), I absolutely love what this is.
The sacrifice of four souls for The Ritual of Awakening is going to be immensely heavy since the PCs hold the few they have very closely, and may lead to a side quest of sorts to be able to gather more in the chance that they won't have enough. I like this a lot.
I really appreciate how open this is in terms of my ability (or rather, privilege) to add details to the individual rooms of the "dungeon" such as monsters and loot and whatnot. One of my favorite things about Mörk Borg (and OSR TTRPGs in general) is the simplicity and openness to interpretation that a lot of the content allows.
This is very well done, according to my tastes, and as an offering in general. I look forward to playing through this as this would make for a fantastic late-arc episode and an extremely impactful one, at that. Nice job, much love.