This is not OGL compliant and I love it. The replacement characters are very cool and on-brand.
Layout's pretty basic and could use some page breaks to keep things organized. I'd have appreciated a map or some procedure for moving from one area to another inside the temple. I think doubling down on the temple and its eldritch transformative nature would make this stronger, as cool as the Soviet antarctic base is. A table of intrusive fantasy adventure thoughts would've been cool - things for players to write down on their character sheet.
I've been deep in early D&D history lately and I think not having a fire hose hooked up to a tank of holy water at the entrance to the temple is a missed opportunity.