Very cool! Obviously lots of entries tried the "multiple characters in distinct worlds controlled simultaneously" thing, but in first person it's much cooler. I like how the big Cthulhu head is visible in all worlds as a sort of orienting landmark.
I think it also visually looks a lot better than most 1st-person jam games that I've seen, possibly because you picked a theme/setting that lets you get away with a big empty void stretching off in all directions.
Overall, one of my favourites so far!
(Also, there's no "g" in "rejoin" in English)