The spells are confusing. It took me a moment to realize that they required a containgen level. It's quite possible that you explained it in the beginning and I didn't read it. More than 2 or 3 screens of explanation and I tune out, as it delays the time to get to the game.
Also, if you could change "Unlocks at stage 5" to Unlocks at stage 6. Finishing the stage v starting the stage are different and it feels disappointing.
Solid game so far.
Viewing post in Night of the Idle Horde (v 0.1.5.2) comments
You expect a boost at the start of stage 5, and don't get that, because it doesn't actually unlock - letting the player's expectations down
Eg make it say what the actual unlock condition is so as not to wrongly mislead people. And if the unlock condition isn't currently correct, then change the condition so it matches the text.