Don't all the cards in Alchemy also change the number of supply piles in the game?
Young Witch changes the number of Kingdom cards and is the only card that does that. Potions are not Kingspdom cards.
Cultist, Marauder, and Death Cart change the number of piles.
And, going back to Mountebank, Death Cart also gains two cards when you get it.
Port is the only 12-card non-victory pile in the game.
Rats is the only 20-pile in the game.
Ruins are the only pile that changes its contents from game to game.
Pillage is the only card that lets you look at your opponents hand.