Elixir
Treasure, $2PP
+P
When you play this, +1 coin for every two actions you have in play
This is probably fine. Instead of +P, it might be good to give +buy though, because you already need 2 Potions to buy Elixir, you don't really want to get it before you're drawing your deck every turn and you probably don't need to have three Potions every turn. The +buy would guarantee that at least it's always going to be useful for payload in engines with a lot of components. It might turn out to be too strong with the +buy, but I would test it with it.
Fountain of Youth
Action, $1PP
Play an action again that you already have in play. Then choose one: either +1 Card per P in its cost; or +$1 per P in its cost.
This draws your entire deck and gives you infinite $. You would have to restrict it to cards other than Fountain of Youth to prevent this from happening, and if you do that, it becomes almost entirely useless — you'd rather just buy another copy of whatever card you'd want to play again because it's certainly cheaper than $1PP. I don't think this idea can work.
Alchemist's Lab (I'm looking for a different name for this one)
Action, 2P
Reveal the top 2 cards of your deck, then put them into your hand. If either of those cards has at least one P in its cost, +1 Action
The problem with this is that it's weaker than Laboratory despite being more expensive than Laboratory. It might be strong enough if you make it draw 3 cards instead of 2.
Werewolf
Action—Attack, $3PP
Each other Player reveals cards from the top of their deck until they reveal one that costs from 3 to 6PP. Trash it and discard the rest. If the discarded cards include at least one:
Action, +2 Actions
Treasure, +$2
Victory, +2 Cards
This is probably too expensive for the effect, and certainly very swingy. At worst, you can hit a Silver on top of your opponent's deck and then it's just an incredibly expensive Saboteur, or you can hit your opponent's Werewolf in which case your opponent can just immediately resign the game.
Alchemist's Seal
(I got the line for the reaction by using a bunch of spaces w/ strike-through)
Action—Reaction, $2P
Reveal the top card of your deck. If it is an action or treasure, play it. Otherwise, discard it.
When another player plays an attack card, you can reveal this card to set it aside, then set aside the top card of your deck face-down. (You may look at the card.) At the start of your next turn, reveal the face-down card. If it is an Action or Treasure, play it. Otherwise discard it. Then discard this card.
I don't think I would ever want to have this in my deck. The top part is significantly worse than Pearl Diver and the bottom part, and the bottom part is exactly the same as the top part except it just decreases your hand size which can be useful against Militia sometimes.
Alchemical Notes
Action, $5
+1 Card
+1 Action
While this is in play, all cards in the supply cost P less.
If there aren't any cards in the supply that cost potions (i.e. most of the time), this doesn't do anything.
Research Grant
Action, $5
+1 Buy
+P
While this is in play, when you buy a card, you may trash this card. If you do, gain a card costing less than the card you bought.
Again, if there aren't any cards in the supply that cost potions, this is incredibly weak.
Test Subject
Action, $3P
Trash a potion. If you do, reveal your hand. Gain a card costing up to twice the number of P in the cost of the cards in your hand. If a card in your hand has more than one P in its cost, +$1.
In practice, this card is probably going to play out roughly like this:
T1: buy Potion
T2: buy Silver
T3: buy Test Subject
T4: buy whatever
T5: you have Test Subject, you don't have a Potion in your hand though, buy whatever
T6: buy Test Subject
T7: buy whatever
T8: buy another Test Subject
T9: draw both of your Test Subjects without a Potion, buy whatever
T10: buy whatever
T11: The best case scenario happens: draw all three Test Subjects with your Potion. Finally, you get to play your Test Subject! So you play it, trash your Potion, gain a card costing up to $4, but wait now you have three entirely useless Test Subjects in your deck because you no longer have the Potion. Why did you even buy a Potion in the first place when you could have gotten that $4 card on turn 1 instead of the Potion?
So, in other words, it's way too weak. You need 5 Test Subjects and a Potion in your hand to gain a Province, and you could get a Province with just 4 Silvers (and if you had a Potion in addition to the 4 Silvers, you would get to keep that Potion, too). Silvers are a lot easier to acquire than Test Subjects and they're always available. In the occasional game where you have Test Subject and another Potion cost card in the kingdom, you might end up in a situation where you can draw your deck while you still have a lot of Potion cost cards in your hand, in which case you might want to get a Test Subject to trash the Potion and gain another card, but that's essentially replacing the Potion with a Test Subject and gaining the card that you're going to gain with Test Subject which is only marginally better than just buying that card instead of Test Subject, and as I have stated before, you can't rely on other Potion cost cards being in the kingdom because usually they won't be there.
Enlightened Township
Victory, PP
Worth 2 Victory for every 3 cards in your deck that have one or more P in their cost.
So if you manage to get 6 of these, they're worth 4 VP each. That's not a lot of VP for a conditional alt VP card which is probably roughly as expensive as Province.
