I like the idea of Magic Symbol. It basically gives each player a unique power, allthough still tied to a specific kingdom card. Very neat combination of a new mechanic with classic dominion gameplay. I'm not sold on exactly how they work, and i think the balance might be off a bit (but you allready know that). Probably you could do with random tokens instead of cards and have Magic Symbol just say "You get the bonus on your Medallion" or something like that.
Gold Leaf is an Action-Treasure, which i still think is a terrible idea for various rule reasons. You can achieve the same result with a Reaction that you can discard at the start of you buy phase for money (as i did with my
Jeweler).
Magical Arrow reacts on being drawn, which is... not exactly pretty. First, it allows you to play it on practically any occasion, be it another player's turn, your cleanup phase, your buy phase, whatever. Of course some of those need support, but the cleanup thing would probably be the best on most boards either way - hey, 5 cards to draw one is a neat chance. At least, it's not nonterminal like Caravan Guard... Second, you can never really prove when a card was drawn, allthough of course Library does a similar thing. Third, you'll play cards inbetween resolving other cards, which is pretty confusing. Imagine playing Smithy, drawing Magic Arrow first, playing Magic Arrow, drawing two more cards. So far, so good. Now play Ironmonger. Draw Arrow, play Arrow, draw Arrow, play Arrow, repeat a bazillon times... oh yeah, and then reveal the top card of your deck and do the rest of Ironmonger. Also, two lines aren't eaxactly pretty, either. Same for Elixir of life.
I think the idea of the magic token is clever in general - it allows to either pay a Potion cost or not, and getting a better card if you do. Of course, it doesn't exactly translate the same as two different cards, as you only need to overpay once, but whatever. I still advise against combining the overpay with yet another ability that requires a dividing line.
Magic Sword is probably the cleanest implementation of the idea. Call me a square, but i think a card concept is cleaner when it's not mixed with something else. It's like Scrying Pool is "some overly-long-worded, weird Spy variant" instead of "draws all your actions" because the attack was unneccessarily mixed in. In a similar vein, the idea of Magic Hammer's duration effect is allready a nice concept, and the idea to have a card that's better if you overpayed Potion is nice. I suggest to make two cards of that. If not, i suggest switching the order so the "this-turn" effect is listed before the "next turn" effect.
Trinket: Everybody is doing the passing card thing now. I'm still not sold on it, allthough i admit a similar card, LastFootnote's Wanderer, worked nicely in 2-player games. Have you tested it in multiplayer?
In the absence of other Potion cards, Spellbook is a tad weak. You could try it costing a single Potion, or add a buy. Either way, it would be decent enough at picking up copies of itself simply for the Market/Peddler aspect to be worth it. Woah, it's simple and i still complain about it. Sorry for that, i hope it's at least a bit helpful.
When Tinker is the only Reserve card, it does nothing but pick up copies of itself.
Capitol's non-Duration clause is really weird. If it was something more common that actually influences the way you have to play (like "an attack card"), i'd say it would be neat, allthough i'd still make a different card of it. Durations are just much too diverse in what they do to actually feel like Capitol influences how you have to play. That aside, the VP aspect is fine, and i guess the card isn't too complex with it. I'd still remove the Duration clause or do something else in that vein on another card.
Warlord + Big Money, hooray! No, seriously, trash engine components, play Treasures, repeat.
Wizard's penalty again is something that won't matter quite often, and i'm not sure why it should be there. It's like the attack-gaining aspect of Squire, just that Squire is much simpler than Wizard.
Mountainer is nice. I like it.
Queen is an Oasis that attacks the first two times. I don't think it's strong enough.
Rook will very often be useless, either because the referenced cards are not on the board, or because there are not dual-type cards in the kingdom.
Castellan is worse than
Swindler (edit: of course i mean) Smugglers in my opinion, because you don't even know what you'll gain before you play it. Sure, with multiple players it gets better, but that still doesn't excuse costing it at more than $4. And yes, it interacts with itself, but that's neither a plus nor a minus, as you can just as well unwittingly give a bonus to another player.
I think Dame bridget is okay, but probably the Bridge effect itself is decent enough without influencing the attack. (Edit: oh, man... BRIDGEt... Have +1 just for that pun)
Dame Regina could probably cost $5. One point per play isn't that much, allthough of course Knight games take longer.
Sir Robin should totally run away.
Rewind seems... Oddly familiar.Enchantment will play the card infinitely.