Honestly I love the idea of this game, but there are a lot of minor issues with the current implementation that really kill the potential fun of it.
The game moves way too slowly, and there's no way to speed it up through manual intervention as far as I could tell. Most incrementals are also clickers and some have management mechanics to give you something to do, but this one you basically sit and wait for the number to hit a threshold, and that takes a long time. This might be because of a bug, which I'll get to in a bit.
I think it doesn't help that you can only have one summon at a time, so you have to build up enough forbidden knowledge to unlock the next to increase your rate, which requires unlocking a bunch of items to hold that knowledge, which altogether makes the beginning of the game feel like a slog.
Sanity doesn't work as described, and feels a bit half-baked. The description makes it sound like there is a chance of losing sanity on each tick and it's higher with stronger summons, but as far as I can tell you just lose sanity by having more forbidden knowledge than you can hold. You can buy items to increase your sanity cap, but there's no way to regain sanity, which I would have liked to have seen (although maybe it makes sense as a hard end condition). If sanity worked as described I'd also really like to see items to decrease your chance of losing sanity.
I didn't try it on mobile, only on desktop, but the UI is really awkward and in a game that's basically all UI, that's a problem. The biggest problem is that it's in this little window that you have to scroll up and down, which is in a page that scrolls up and down. Unfortunately I think this is where the desktop experience was sacrificed for the phone experience, because I can see how this would work on a phone. Even still, I'd have preferred the 3D view and tabs to be fixed in place and only the submenus to be scrollable.
The game is pretty buggy in its current state. The biggest problem is that the tickrate seems to be all over the place. Sometimes the forbidden knowledge rolls in quickly, sometimes it trickles. There are also issues with the UI sometimes not responding to clicks on the buttons, or taking a few seconds for it to register.
While all of these are pretty significant issues for the game, I think most of them could be fixed with only minor changes. Tweak the numbers, maybe add a clicker mechanic, tweak sanity a bit. The biggest challenge is going to be that tickrate issue. Once again, I really do like the concept and the aesthetic of this game- it's got a neat dark fantasy thing going on and the graphics are simple but appealing- and I think it could be a neat little incremental if those crippling issues are worked out.
EDIT: I also do echo the sentiment that I wish this game had background music built in.