This has been updated to match my "Signature Weakness Project." I have done my best to make sure that the original content isn't altered too much, out of respect for any comments.

A very investigator-focused signature weakness. Looking at the two elements, the effect and the discard condition, we get:

The effect: At the start of a campaign, this card eats up about 4 actions, blocks Dr. Fern from useful horror healing, and messes up her economy for at least 2 turns. Which is pretty severe. The only way to mitigate it is get better horror healing, which comes with XP. A the start, horror healing acceleration is limited to Logical Reasoning, Soothing Melody, and Hypnotic Therapy. As XP accrues, 2 point healing gets reasonably common (which can be boosted to 3 with Hypnotic Therapy), and Logical Reasoning (4) can clear it in one action, if you have 2 clues. Ancient Stone:Minds in Harmony (4) can even do it as a reaction, assuming you can get 4 secrets on it and draw 4 cards. I personally like the idea of Kerosene, just because it seems like such an extreme therapy.... In most cases, a reasonably experienced Carolyn will clear it in 2 actions, which is not too bad.

The discard condition: Heal 4 horror off it, which, as noted above, gets easier as XP accrues.

When you think about it, this is an average signature weakness, maybe barely above average at low XP.

Box vs book It's better than To Fight the Black Wind in most situations, and it's paired with a much more useful signature asset, so most player will chose the "box" pair rather than the "book" set or doubling up, especially since having this and the Black Wind out at the same time are a horrible synergy.

This has been updated to match my "Signature Weakness Project." I have done my best to make sure that the original content isn't altered too much, out of respect for any comments.

Another weakness aimed square at the investigator's special ability. Looking at the two elements, the effect and the discard condition, we get:

The effect: You can't add assets to the play area. Dexter likes putting assets into play, it's kind of his jam, and this card stops that hard (see the note at the end about interpretation of the text). This is another very situational weakness. While you are never happy to see your demonic "friend" show up, sometimes it absolutely wrecks you, while other times you can limp to the end of the scenario without too many regrets. In some ways, it the exact opposite of Searching for Izzie or Cover Up, in that, if you have to draw it, the last turn or two is when you want to do do so. As usual with the to remove weaknesses, this has much greater impact in solo than multiplayer.

The discard condition: Spend two actions.

Taken together, this is a below average signature weakness, maybe average in solo.

Box vs book While this weakness is probably less annoying overall than Occult Scraps, the "box" signature weakness, neither is too terrible, making Dexter one of the investigators who should think seriously about including both sets of signature cards in one deck.

Note: The card text is a bit puzzling, since it seems obvious that the meaning is that Dexter cannot add assets to his play area. However, the Rules Reference makes clear that "play" and "put into play" are completely separate actions, suggesting that Dexter is only forbidden Anna Kaslow and Sleight of Hand, which would require creating an entirely new tier of "This is barely a weakness." When asked about it, MJ Newman responded "The intent is that you cannot do either—play assets or put them into play—the idea being that playing something does in fact also put it into play. However, as you rightly point out, that’s actually incorrect as far as the rules are concerned, so we’ll be updating the rules to reflect this in a later edition of the FAQ." So, Yaztaroth prevents any assets for Dexter.

Comparing this with the "book" signature asset, Molly Maxwell, it's hard to say which one is better, since they do such different things. This is a nice example of a card tailored toward its investigator. It's cheap and adds a valuable boost to what Dexter wants to do -- put Assets into play, use them and then discard them. He can drop a Flashlight at the very start of his turn, assuming he has another Asset to discard, investigate 3 times with an effective 4 and -2 shroud, then start the next turn playing a .41 Derringer to blast away with 7 against an enemy who popped up during the Mythos Phase. It's not flashy, but it's better than it looks at first glance (which is pretty thematic for a magician).

Since it really has no competition with the "book" signature, Dexter is pretty well placed to take both.

I like Molly. Her cost of 3 is about average for a Ally, she has some decent soak, and can get you 3-4 named card draws if you are careful about the Assets you use. It's worth making a list of their unique traits, so you know if you want combat, you say "firearm," if you want your Shining Trapezohedron, you say "relic," and so on. The only drawback is that most of the spells have only the trait "spell," so Molly is just going to hand you the first one she finds, which isn't great if you wanted Sixth Sense and you get Spectral Razor instead. However, if you are judicious in your selection of Assets, keeping an eye on traits, you can get pretty close to making Molly a four use No Stone Unturned (5), which is not bad. She also does not get in the way of the "box" signature Showmanship, which puts Dexter in a pretty good place to take both sets of signatures, if you dont't mind a thicker deck.

the only dual trait spells available to Dexter are: Blood Pact (pact), Eye of Chaos (cursed), Seal of the Seventh Sign (ritual), and Song of the Dead (song), none of which particularly scream "Dexter!"

[edited at oct 16, applying errata]

This card's effect is quick strong; Amanda cannot use a skill card during one round, and her net stat is reduced by 1 (from errata, commiting card is not optional but mandatory Forced one).

However, this weakness does not have any terrible panelty like other weakness skill such as returning if failed or commiting only your test. Thus, to avoid significant penalty, you just commit this card at ANY test before start of investigate phase. -1 skill value for one test is neglectable effect.

Here are several ideas:

• Search your deck and/or draw many cards: If you draw this card during your turn, it's ok you just commit this. Mr. "Rook" is suitable for this. You can search 9 cards, and draw this for free. (But 4xp with taboo)
• Commit during mythos phase: If you draw this card during upkeep phase, only chance is mythos phase. It may be a better choice that you commit this at encounter test. If a encounter doesn't have any test, you may want to find a test for this. Some cards make you initiate a test at any window: Cipher's ability, or Expose Weakness (if a enemy in your location). You have a window just before the end of mythos phase.
• Keep her signature and replace: Obscure Studies can be an emergency button. If this weakness exists beneath Amanda, play her signature and commit (returned) this weakness.

Taboo version of Scroll of Secrets can be another solution. You may trigger that ablitiy during upkeep phase window, and you can place 2 of those card on top of your deck and those card is drawn at upkeep phase & beginning of investigation phase.