Oh, also, your game doesn't appear to have a good way of coping with the worst parts of upgradable deckbuilding gameplay. I mostly win by making a God Card and then thoroughly thinning my deck around it.
Won last game with a Scorch that dealt 110 dmg three times, drew 3 cards, and cost 0 energy. Paired it off with cards like the exhaust-1-draw-2 card. At a certain point it stopped being deckbuilding and more turned into MTG Blue Gameplay of "How can I thin this deck into nothing, and then redraw my murder button until my opponent dies without ending my turn?"
Feel like cards in-theme should have some kind of mutation chance the more they're trained, or some kind of max stat growth. I like the snowbally nature of it all, but I was rewarded maybe too much for making Scorchcalibur and throwing out everything else.
Draw effects should apply before the card enters Discard, to prevent mill redraw off a single card effect.
If you go the mutation chance, could make metaprogression about expanding the caps or reducing the chance. Mutation could offer transmutation potential into interesting cards with a risk of duds (another thing you're missing that would make a lot of sense for the fungal theme - random transmutation rather than evolution-based transmutation).
Also, I feel like enemies should have some way to counter extremely potent max damage cards other than their current shield mechanic. It's solid for it, but there's nothing that prevents me from making my big card murder 3 times over.
Also, there's just some cards I can't Frog? I don't know how I'm supposed to tell which are Froggable. Specifically looking at the broken armor one, that generates Tantrum? I didn't like it and I wanted it out but it just Isn't Froggable, and that sucks. I eventually had to Frog Potion it.
Setting aside combat: Explore deck.
Search needs to exhaust, not discard. I put 3 Searches in my deck and it let me mill out every energy extender I could get until I pulled out my training dummy and frog cards.
Also, all plinth cards should exhaust too. It makes sense to me if we're going to have it be possible to reshuffle the deck - ESPECIALLY if you intend to make plinths non-renewable; why would I want to risk a Frog or Training Dummy resurfacing when I've already used my plinths? What a waste of a search!
I love Search for its redraw potential, but it's way too potent in current state. It absolutely needs to be a once-per-explore-per-card.
On that subject, Scavenge is great. I like its utility of mainly producing Consume effect cards. It feels really good to have without being overpowered. Paired with good draw cards, it shines nicely.
I think the game is a little clunky right now (some monsters are inherently Timid without the status being applied at all times, for example) but it looks like a pretty good proof of concept. Hope to see you come out with a finished version soon!
PS: If you decide to stretch out testing new concepts, can I suggest adding more applicable debuffs? I'd love to see some interesting debuff manipulation beyond what Vulnerable already offers me.