Pretty massive bug with transcend count. Every time you transcend it stays at zero and adds one to prestige count instead. Makes two of the early mythos upgrades perfectly useless, as they're tied to number of transcends.
I would have to strongly second the suggestion to conveniently buy every character's health up at once. Other than that: really solid entry to the genre. Interesting approach to multiplayer aspect. I'd really love to see more co-op features. Raids? Mutually exclusive upgrades that synergise with each other between friends? There's a lot of potential.