I generally find the Ritual Candles to be an (cheap and less effective) equivalent of Dark Horse. Let me explain. The Ritual Candles gets you +1 on roughly a fifth to a third of the Chaos Bag, so at best, it's equivalent to +0.2 to +0.33 static boost to all your stats, for 1 resource, which is not bad. For example, it's 25% of the Core Set's normal difficulty chaos bag.

I tend to find better than any other class just because they are the only class capable of using so easily all their slots (hands, arcane, body, accessory, ally), they have a level-0 to enough cards of each slot-filling type.

As of today (end of Carcosa), I don't think there's much level-0 cards to fill in your hand slots to begin with. investigators can actually use the Flashlight and the Knife but most of them do not need more combat (Agnes) or clue-gathering (Marie) abilities. So If you're looking to optimize slot-filling your investigator, you should definitely consider the Ritual Candles, at first.

However, though I think it's an underrated card, it certainly isn't top-tier, that's why I recommend swapping them as soon as possible with the Spirit Athame, since you're usually performing Spell tests anyway.

I think the FAQ

Any investigator at the same location as "Ashcan" Pete with Wracked by Nightmares in his threat area may trigger the to discard it, as per the FAQ [V1.0, section 2.1].

Is wrong, first it's section 1.2 in the newly released FAQ (V1.2), and it does state

An investigator is permitted to use triggered abilities ( , , and abilities) from the following sources:

• Any card that explicitly allows the investigator to activate its ability.

which it does not since Wracked by Nightmares reads

: Discard Wracked by Nightmare

and further

• A scenario card that is in play and at the same location as the investigator. is includes the location itself, encounter cards placed at that location, and all encounter cards in the threat area of any investigator at that location.

which also does not apply here, since this is not an encounter card.

This may seem scary because it targets Mark's sanity, which is low. But I think that, on balance, this is one of the mildest weakness any investigator has. I would never trade this for Cover Up, The Dirge of Reason, or even Smite the Wicked were the option available.

Of note here are a few things:

1) Since it says "for every 2 damage," Shell Shock rounds down. 1 damage on Mark = 0 horror from Shell Shock. The great majority of the time, this card will deal 0 or 1 horror. Not scary at all.

2) Mark was already incentivized to keep the number of damage on him to a minimum because of how Sophie works. 6+ damage is the point at which Shell Shock starts to get awful, but Mark can avoid ever getting into that position. He should be aggressively killing monsters before they attack him, he should run healing cards, he should be playing assets to soak up damage for him, and he should be judicious in his usage of Sophie. If you're playing Mark sensibly, it's very rare that Shell Shock will deal more than 2 horror.

3) Shell Shock is extremely predictable (unlike, say, Final Rhapsody.) You know exactly how much damage it would do if you were to draw it. That means if you're ever in the death zone for Shell Shock you will know that ahead of time. You or a teammate can then heal some damage and/or horror (and most Mark decks are full of cards that do this), or Mark can play an asset that soaks horror.

4) Shell Shock doesn't deal direct horror (unlike Abandoned and Alone). All Mark decks are going to want to play horror-soaking assets, and quite possibly two or more of them. This means Shell Shock can still be manageable even if Mark has accumulated a lot of damage.

5) All in all, Shell Shock is one of the most likely of any player weakness to be discarded for no effect (other than wasting a draw, as all weaknesses do) or a very minor effect.

A terrifically powerful card, and at the right price. At lower difficulties, this can allow you to auto-succeed a Fight test by spending 2 ammo and pitching (Vicious Blow) or pumping (Physical Training) enough to beat any negative token in the bag. At higher difficulties you can still do this, it just takes more ammo/pump. Additionally, the cost to play is within affordable margins for any non-Zoey Guardian, and the xp cost is super reasonable. The icons are significant as well, since they buff the two ways an investigator deals with enemies (good for evading if the enemy can't be killed), and as a Tactic card, it can be placed beneath Stick to the Plan (although personally I feel there are better options for those precious slots, like Emergency Cache, Ever Vigilant, and Extra Ammunition).

As some people mentioned, this card is a good replacement for Manual Dexterity. Same number of icons. It's worth remembering that Resigning does not provoke attacks of opportunities. If you are engaged with ennemies, have low health/sanity and are about to die, you can play this card even if you have no resources left to avoid getting a Physical or Mental trauma. That said, will not work with all scenarios. Would be interesting to see stats per campaign.