The Harbinger essentially disables your deck, which is such an interesting effect for a weakness. I've been trying to think of ways this card could be used to Norman's advantage.

While the harbinger is in play:

• Any ability that would have no effect without deck interaction cannot be activated [^1]

  (You could not activate Word of Command—naming a Spell Card does not alter the game state)

• Any cards with additional costs which interact with your deck cannot be activated [^2]

  (You could not trigger an attached Bloodlust)

We can only play cards that would interact with the deck if the deck interaction is not a cost of playing the card and they have some other effect on the game.

Improvised Event Recursion

The first thing that sprang to mind was Winging It. If you have harbinger on the field, you could infinitely play this from the discard pile, granting an endless 1 cost source of -1 Difficulty, +1 Clue Investigate actions!

(The reuse would also be applicable to Improvised Weapon and Impromptu Barrier, though I can't see Norman purchasing Versatile for either)

Winging It does not exclusively interact with the deck. It starts an Investigate action. The deciding factor on whether this is possible then, is whether the "If you do, shuffle it into your deck after resolving its effects." clause is an additional activation cost when you opt to play it from the discard pile.

• "You owe me one!" has the same wording with no "after" timing. The card's effects are not dependent on drawing. You would still be able to play an ally's card if one or both Investigators are unable to draw. This event is still be playable.

• Enchanted Blade is even more similarly worded: "you may spend 1 charge... If you do, you get +1 and deal +1 damage for this attack." If something were preventing you from increasing your or damage, I believe you would be unable to spend a charge to empower the blade, as the game state would not change apart from paying a cost. If boosting only 1 of either the +1 or +1 damage was blocked though, there would still be an effect, the optional cost should be payable, and the empower effect activate-able.

Given these 2 cards, I'd argue that shuffling it into the discard pile is an unresolvable effect, due to the Harbinger, and that Winging It is thus playable.

Discard Without Drawing

We could play Blood-Rite to discard cards without drawing, or Knowledge is Power to discard Spell or Tome assets from our hand without drawing cards.

I struggle to see how it could be beneficial for Norman though.

Encounter Protection

Any Treachery that would interact with your deck simply doesn't.

This has limited usefulness in most scenarios, but can be of immense benefit in some specific campaigns. It's hilarious to draw encounter cards that just have no effect due to the deckless playstyle.

Cost Rulings

[^1]: An ability cannot initiate ... if the resolution of its effect will not change the game state.

[^2]: If an effect that requires an additional cost would resolve, the additional cost must be paid at that time. If the additional cost cannot be paid, that aspect of the effect fails to resolve.

One of the more "head-scratching" signature weakness, it definitely plays to Norman's "flavor," both mechanical and fictional. Looking at the two elements, the effect and the discard condition, we get:

The effect: This locks Norman's deck, preventing anything that would interact with the deck, so no drawing, searching, or anything else. This is generally pretty bad for a like Norman, although, if it comes out very late in a scenario, it can be ignored as you race to the finish. It's kind of the reverse of Roland and Jenny's weaknesses -- if you see those late, you are usually doomed, but, if they come out early they are more nuisances. Since messing around with the top of his deck is pretty much what Norman does, if this comes out earlier than the penultimate turn, you need to grit your teeth and clear it pretty quickly. Occasionally, you will get the mild satisfaction of seeing some encounter deck effect (like the Dunwich milling) fail, which is fun, but the sooner cleared, the better. There isn't really any mitigation you can do.

The discard condition: Spend . Since it functions "as if it were in your threat area," another investigator can clear this in a pinch.

All in all, this is an average, maybe below average weakness. It's not going to cost you the campaign, but Norman could be defeated if this got drawn while he was low on cards and in combat.

Box vs book This is a bit more persistent than Vengeful Hound (which has a similar effect, plus biting), but Livre d'Eibon is better than Split the Angle, so the "box" set sees more use, although you can run both without too much trouble.

DEFINITELY a lot milder than Norman's other weakness, which wasn't too much to deal with in its own right. is generally the cost to rid oneself of a weakness, so this fits right in there, and you probably are going to get rid of this as fast as possible - I mean, look at its effect, why would you NOT - so if this spends more than a turn plaguing you, you're... probably doing something wrong. No offense.

In any case, the Livre d'Eibon is so much better than Split the Angle, so it's a small price to pay for a MUCH better Signature.

I personally think that a Norman deck should be running Eureka, Foresight, Parallel Wills, and Scrying because there's just so much synergy between those cards and his ability. That said, it won't always be possible but you would be able to get around Harbinger if you ever caught it in a scry or parallel wills - make sure to Eureka when you know it's in the top 3 cards and name it with Foresight ahead of time (per FFG it looks like for Foresight and "Search and Draw" effects they want the timing window to be prior to the search part). If it gets to the top of your deck normally you can't Foresight it since it prevents itself from being drawn, but if you can draw it from inside your deck that bypasses the limitation and Foresight cancels it before the Revelation effect would put it on top of your deck.

That said, if you know it's coming you can also just prepare for it and time the "draw" when you know you can spare the two actions, but that combination of cards does let you skip having to deal with that and is worth noting I think.

While The Harbinger is revealed and on top of your deck, cards in your deck cannot be {{searched, drawn, or manipulated in any way}} except by the below ability.

so Can Occult Lexicon be blocked? Because I can't search my deck