Replayed a bit, and here are some more thoughts:
Suggestion: add an NPC in the temple that grows when you upgrade the temple. No need for special interaction or anything, but it's a expansion fetish game. So if something can be upgraded, an NPC must grow with it.
Recommendation: DoT should trigger at end turn not turn start, reason is simple: an single enemy is left with 4 HP and is poisoned/bled. He will automatically lose once the turn start, but I still need to select my actions; hence time wasted. If the poison/bleed triggered at end of the previous turn, I would skip the pointless player turn, and in effect it would be identical (AFAIK, there is no action possible in the action pile between the end of turn and the trigger of poison/bleed.
Each of the growths has a flaw:
Demon: she gain level by absorbing level. So it's better to stay low level and feed your low level by entering/exiting dungeon. You can easily find the spot where you gain as much level as it consumed by staying low level. (Possible fixes: 1) she stops draining if your level gap is too big; 2) (better option IMO), she stops gaining level if the level gap is too big. She still lower your level but she doesn't gain anything)
The nightmare are rapidly annoying. You should add a way to (semi-)permanently remove them by winning and a give up option during the fight.
Knight: her growth system isn't bad but far too slow. I have maxed nearly everyone but her is still at stage 2. Since the combat are very fast and offensive oriented, she doesn't gain a lot of rapture per fight even when you aim for it. (Possible fix: divide the requirements by at least 2, maybe even divided by 5)
Fox: the opposite: she is very cheap to grow. You only need around 50 herbs sold at 250g, so 12 500G. To reach the village, each fight give 750G. So, in only 17 fights, you have enough to max grow the fox. Possible fix: 1) only a limited non restockable amount of herbs is buyable, 2) herb cost increase exponantially.
Slime: no problem with the permanent grow. But the temporary grow is rather pointless: fights are finished in only a few turns (both players and enemies deal a lot of damage, there isn't a real tank enemy), so she barely grow. Possible fix: her growth is a sort of mana bar that stays between combat. You lose part of it after each fight but not everything. (You could even make it more difficult to grow to force the player to keep fighting to reach max growth)