Does the additional cost of 4 leylines have to be paid from the investigator's resource pool (making this effectively cost 6)? Or is the reference to 'cost' because it cannot be played if there are less than 4 locations in play?

This is new boost + resource asset type. It seems that this serise is similar to PT4 serise. However, the purpose of both are quite different. 1) PT4 doesn't give any cost, but this do. 2) PT4 can boost your skill at encounter card, but this cannot. 3) PT4 can boost your skill with your resource, but this cannot. Therefore, if you're plan to boost your skill value, it may be better to use PT4.

Guardian(): Most guardians don't consider this. If you check the available list in guardian pool, there is only 1 asset to boost and most cards are event. It means that it's hard to spend resources on Prophetic for each round. However, if you're plan to use Boxing Gloves such as Nathaniel, Prophetic is good candidate. Also, Prophetic is the only asset working with Gang Up. Prophetic + Gang Up is 1 resource cost with +3 with 4 damages.

Survivor(): Like guardian, there are very few asset; available list. However, there are many good Fortune events: "Look what I found!", Lucky!, Will to Survive, True Survivor, Eucatastrophe, Trial by Fire... Thus, you can use Prophetic as an economy card. If you want to play True Survivor repeatedly without On Your Own, Prophetic is good solution.

Mystic(): Prophetic works with Spell. That's all. However, if your deck has lots of resources like P-Agnes or Dexter and you want to use Propertic as an boosting source, Arcane Studies 4 is usually better.

Off-class cards: available list I don't know which cards are good, but some economy cards work: 21 or Bust, Hot Streak.

When you see this card, your mind probably immediately jumps to Guardians. After all, they love their guns and fight boosters. And they tend to have expensive guns, win-win right?

Well... not so fast really. Guardians already have fight pretty darn well covered, and this isn't going to be a better option than most tools they can take to serve as a fight booster, especially at 3 XP. Between your base stats, Tarot Cards, Friendly Local Officers, and Evidence on a stick a guardian can easily sit at a fight value of 6 before their +4 from their Flamethrower comes into play.

Guardians also have expensive weapons, but they tend to play a singular weapon due to both how powerful their 5 xp suite are, their ability to keep it topped off with reload cards they can ensure are sticky and the strength of their tutoring. Guardians with the right mulligan policy can force their big expensive 5 XP weapon on the first two turns. So you really can't view this as a discount card for them.

Charisma to run more of your +fight allies, Reliable, Ace of Swords, heck, even Physical training (4) all kinda low key do what this card does but better? If your looking at this as a chance to really boost one attack with one card (say... you are running Shotgun for some reason and you really want to make that initial hit slam someone), you even have stuff like Enchant Weapon which for most guardians is just better and blows this utterly out of the water for weapon usage.

I am sure a guardian deck is out there that may want to spam niche weapons with huge burst swings and plays lots of armor cards too (Old Shotgun decks with pocket fulls of grenades maybe?) but overall this is just questionable in the guardian pool. Some of the tri-class 'pick a tribe' cards are economy cards, but these 3 assets are not spammable in guardian, so it really comes down to being a booster card in guardian, and guardians just do this better, and while this can stack with them, are you really going to need more than 8 deckslots dedicated to passive boosting?

I would say the most compelling case for this card is in the rogue class, though some survivors may want it as well.

Rogues can get really good at fighting, but struggle for static boosts, especially with how almost every slot they have is highly contested. They are less likely to power upgrade their weapons because while they have good higher end weapons they are less able to force them into their hand than guardians, due to lacking Prep for the worst and Mr. "Someone deserves a raise for figuring out this pun name."

A lot of rogue weapons and strategies reward you for playing more than one weapon over the course of a game, due to their low ammo counts and come into play effects, and while this won't give you discounts with Sleight of Hand it will fit nicely into sleight of hand style decks. After all, if you are running sleight of hand you eventually plan to PLAY that gun you keep flashing. And you often want to 'over-succeed' on rogues, so having a boost can really matter.

And, of course, there is the base stat gap. Even if rogues COULD run as many slotted boosters as guardian, most rogues have fairly low fight values, despite being a fighty class. They make up for it a bit with a lot of fantastic skills and events and draw to fuel those skills, but between their lower weapon bonuses and lower stats it can take a rogue a bit more effort to get to where they are hitting as often as a Guardian, let alone succeeding by whatever.

Survivors can also get some value out of this too. One unexpected candidate for this card is everyone's favorite 1 fight orphan herself, Wendy Adams, is a strangely great candidate for Bruiser, because she can combo this with her famous fireaxe to get much more serious value out of those free resources, or use it to push her attack value up to 9 for a swing.

Every single one of these cards is going to feel different just because the flavors of these tags matters so much, but I think for bruiser the question isn't going to be 'do I like weapons and maybe armor?,' because this doesn't really help those in generic cases that much. Instead, the question is 'Do I need a fight boost but lack access to one in slots I can safely give up, or am I going to be playing 3+ weapons in a game?'

War of the Outer Gods Veteran Gloria Goldberg with True Magick and Sign Magick is the hell of a medium. Use Sixth Sense to gain one or more clues, then activate Dreaded End, draw an additional card from the encounter deck and discard 2 + 1 cards. You can't have more controll over the mythos deck.

That is, what Sign Magick is made for. You may have only one charge for charge spells (which can be refilled with Twila Katherine Price) but you can activate Wither / Wither or Sixth Sense / Sixth Sense without the need of charges.

True Magick is all your spell assets in your hand at the same time for the purpose of activating them. And True Magick is "under your control" for the purpose of Sign Magick.

So keep spells in your hand. You cast from your book. Quite cheap and effective.