I just don't see a place for this card. Compared to Obfuscation:

1) It's slow (takes an action to play, and hence, is prophylactic).

2) Requires tokens to be in the bag (and requires you to seal them, foregoing their benefit).

3) Has the same resource cost; takes up the same arcane slot; has the same "Spell" trait.

4) ..and costs 2 XP instead of 0 XP.

In exchange for all that, Shield of Faith cancels any attack, not just AoO's; and works for any investigator at your location.

So among investigators who can take both (Leo, "Skids", Zoey, and Lola), you'd clearly only be interested in this if you're leaning heavily into protecting your teammates. And if that's the case...well, there are better cards for that. Dodge, Solemn Vow and Heroic Rescue are all fast and cost fewer resources (ZERO for SV and the upgraded Rescue), require no XP, and the latter two complement Leo's tanky nature. He can certainly afford to take the occasional hit on the chin without sinking some considerable setup into canceling attacks. Skids is a fighty Rogue, whereas Zoey is a roguish Fighter; between the two, I guess Zoey likes this a little better since she's more likely to be engaged with an enemy during the enemy phase. I'd still rather have her resources committed to dealing damage instead of playing defensively, though. And as far as Lola...well, beats the hell out of me. If you're running a Lola bless-heavy deck that can leave a defensive asset on the board just to cancel some enemy attacks--well, that's just crazy, amirite?

Now, a few words about the value of canceling Attacks of Opportunity versus any type of attack. It's been said more eloquently elsewhere, but if you're unintentionally engaged with a ready enemy during the enemy phase, your game is already heading south. characters operate by killing enemies during their turn, and if one makes it to the enemy phase, they have several contingencies to choose from: expendable allies that provide benefits from dying; counterattack events, items, or allies that kill the enemy during its own turn; or some other situational reason why you wouldn't mind taking a hit. Simply canceling the attack with a card like Shield might have some value, but it lacks the forward momentum of these other options, and is therefore the least advantageous.

On the other hand, taking an Attack of Opportunity can sometimes be a necessary evil that you incur as a cost of keeping your tempo in place. Maybe a monster spawned on you during the Mythos phase before you have a weapon out to deal with it, and you need to play that asset from your hand. Maybe you need to drag said enemy to a new location--one with a combat-ready teammate, or a clue that you'll pick up by killing the monster. Or maybe you're Trish, or you're running with Alice, and you like investigating with an enemy in your face. The point is, AoO's are incurred while you're doing something to advance the scenario, not just standing there and getting torn up. So clearly I believe Obfuscation is the superior card among those who can take it--and that's only if you're playing a specific build that will benefit from canceling attacks at all.

And how many attacks are you planning on needing to cancel, anyway? If it's 1 or 2, why bother? Use a cheaper, faster option like Dodge. And if it's 3, 4, or 5...well, Arkham Horror isn't a game that rewards a heavily defensive playstyle. Being a punching bag isn't going to win you any games.

Lastly...what about the guy whose picture is on the card? A who might be interested in protecting himself and his teammates, and who has the ready ability to add blesses to the bag? Even if this card was 0XP--or paid for with bonus starting experience--I'd still pass. Don't forget that you've spent cards and resources to put those tokens in the bag, only for them to wind up in purgatory. I greatly prefer Rite of Sanctification with Mateo, to cycle those tokens back to where they belong faster while getting some assets out for your team: weapons, spells...you know, the type of things to ensure everyone will be taking fewer attacks from enemies.

TL;DR: Leave it in the binder. 2 resources, 2 XP, an action, a card, an arcane slot, and a bunch of sealed tokens just isn't worth it to cancel a couple of attacks.

As a supplement to the other reviews about how to use her amulet, I would like to add one other thing I really like about the amulet, which is that Wendy does not have to use it. You can choose to design your deck with the proper events for using her amulet, but you can also design a deck where you ignore the amulet, take whatever cards you like, and use the accessory slot for some other purpose. She works just fine this way, her main power is quite good all by itself, and her weakness is less meaningful when you are not planning to make any use of the discard pile. So Wendy has a lot of flexibility to design her decks, this card increases her options rather than limiting her to a single path.

The other reviews here just assume everyone knows the knife is bad and tried to defend it, so I am here to write the review of why the knife is unpopular.

If you only own the basic set, you may have so few weapons that you feel forced to take the knife just in order to have enough weapons in your deck. Otherwise, though, while the knife is not an unusable card, it is a hard weapon to like.

If you are a combat character, then a knife would be a ridiculously inadequate primary weapon, you need a weapon that does more than one damage and can be used many times. The only purpose of carrying a knife for such a character is to act as an offhand weapon. The knife is adequate for this purpose, you could certainly get away with making a character like this and have fun playing it. But there are reasons why it just isn't that great.

First, it doesn’t particularly solve a problem. A single shot with the thrown knife just isn’t enough extra ammo to really solve an ammo problem, and the knife, while cheap in absolute terms, is actually a rather expensive way to purchase a single extra ammo. The +1 for the held knife is potentially nice against enemies with odd amounts of health, that would be the reason for holding it, but it still isn’t that impactful on the game. It is only relevant if your other hand is holding a gun with ammo (not your enchanted blade or timeworn brand or switchblade), and it is only +1 – you always have the alternative of just punching the foe if you need to save ammo.

Second, if you have decided to dedicate both hands to holding weapons, you would be better off with a two-handed weapon. They do not publish a lot of low-XP two handed weapons so you may not have the option of never putting any one handed weapons into your deck, but the more campaign expansions you buy for the game the more two handed weapons you will have available and the less likely you are to want a knife whose only purpose is to supplement a one handed weapon.

Third, limited deck space. With only the basic set I was often desperate for any card that would act as a weapon so I might put a knife in my deck for that reason, but now that I have lots of expansions there are always more really cool cards to put in the deck then I have space for, leaving little room for mediocre cards like the knife. And in any case, the number of weapons in the deck is not so large that I can guarantee drawing two of them in my starting hand. Since a combat character is practically crippled without a weapon I would really prefer that every weapon in my deck be a weapon I’d be content to see as the only weapon in my starting hand. A knife just is not acceptable as the one weapon you drew. And if I draw two weapons, instead of one of them being a knife, I would be quite happy to get a second real weapon, use the first weapon until I get more money, then play the second weapon if I run out of ammo on the first weapon.

If you are not a combat character, you could cheaply play a knife to kill rats or as a one shot desperation weapon. The problem is that it takes up a precious hand slot for a weapon you're really planning to never use, you're likely better off putting something useful in that hand and either evading, or relying on your friends to protect you, they will likely do a better job running over to fight monsters than you with your one puny knife throw.

To pre-emptively answer your question:

"[Irish mythological hero/demigod Cú Chulainn] is known for his terrifying battle frenzy, or ríastrad (translated by Thomas Kinsella as "warp spasm" and by Ciarán Carson as "torque"), in which he becomes an unrecognisable monster who knows neither friend nor foe."

I.e.: Hulking out.

(Merely here due to Irish mythology? Or also the influence of Marvel Champions?)

from The Táin (Táin Bó Cúailnge) [translation KInsella]: "The first warp-spasm seized Cúchulainn, and made him into a monstrous thing, hideous and shapeless, unheard of. His shanks and his joints, every knuckle and angle and organ from head to foot, shook like a tree in the flood or a reed in the stream. His body made a furious twist inside his skin, so that his feet and shins switched to the rear and his heels and calves switched to the front... On his head the temple-sinews stretched to the nape of his neck, each mighty, immense, measureless knob as big as the head of a month-old child... he sucked one eye so deep into his head that a wild crane couldn't probe it onto his cheek out of the depths of his skull; the other eye fell out along his cheek. His mouth weirdly distorted: his cheek peeled back from his jaws until the gullet appeared, his lungs and his liver flapped in his mouth and throat, his lower jaw struck the upper a lion-killing blow, and fiery flakes large as a ram's fleece reached his mouth from his throat... The hair of his head twisted like the tangle of a red thornbush stuck in a gap; if a royal apple tree with all its kingly fruit were shaken above him, scarce an apple would reach the ground but each would be spiked on a bristle of his hair as it stood up on his scalp with rage."

Eldritch horror indeed.

(Honestly, I'm disappointed we didn't get some flavor text excerpting a translation.)

Sadly, this card is mostly useless at the moment. I played it through a campaign as William Yorrick with a chainsaw - which seemed like about the best-case scenario for dealing the excess damage. But even after playing it many many times, I still almost never managed to get a single resource on the card.

In order to deal even 1 excess damage, you usually need to spend something that's worth more than 1 resource - like commiting a Vicious Blow, or wasting precious Chainsaw ammo on a weak enemy. The reward just isn't worth the cost, especially when you compare it to Emergency Cache.

All hope is not lost, though. I personally hope that we will see more cards to support this "Overkill" archetype in future. With more ways to overkill enemies, and more rewards for doing so, this could become a really fun playstyle. Perhaps someday there could even be a guardian who focuses entirely on overkilling enemies for big rewards. This could eventually redeem this card, in the same way that Winifred Habbamock finally redeemed Opportunist.

If that day ever comes, I will be incredibly excited to take this card out of the binder.