Time for another first look. I havent had much of a chance to play with these, so first thoughts:
M1918 BAR: Well, this weapon costs exactly the same amount in resource cost and XP as the shotgun, so I can't help but compare the two. The BAR is an interesting weapon, and could be good for heavy damage on a boss, but it's not very good as a "main" weapon. Things that add a set amount of ammo (extra ammo, venturer...) are much less useful on the BAR compared with the shotgun due to the high ammo consumption of the BAR. Contraband is still pretty nice though, allowing for 3 shots at maximum power. Unfortunately, I think the Shotgun is just more viable on most characters. The best character to use this weapon IMO is probably Leo Anderson, because of his access to Contraband and Sleight of Hand. Zoey could pull out the same tricks of course, but it would take some of her valuable out-of-faction card slots. I could definitely see myself taking a "one-of" of the BAR for sleight-of-hand boss killing. 2.5/5 useful in the right build, but for most characters weaker than the shotgun.
Ancient Stone (Knowledge of the Elders): Ah, we finally see the Ancient Stone. Lets just say up front that this requires a huge amount of work on the part of your investigator just to include in your deck. Like other "unidentified" seeker items, you have to upgrade from the lesser version of this card, but unlike a Strange Solution or Archaic Glyphs, the basic Ancient Stone costs 1 xp. Ouch. That means the absolute earliest you can include this card in your deck is scenario 3 because you'll need to first get an experience (scenario 1) and then translate (ideally scenario 2) before you can upgrade. It also means this card basically costs 5 XP, instead of the 4 shown, because you'll have to purchase the Unidentified version first. THEN the number of secrets on this card is dependent on how high the shroud value was. You can have more secrets here if you passed a harder check for the Unidentified version. But that, of course, won't be easy. Because I feel its relevant, I'm going to include some minor spoilers from forgotten age below the spoiler tag:
Supposing you want to identify the stone in scenario 2 of Forgotten age, the location shrouds range from 2-5, giving you anywhere from 5-8 secrets. However I tend to find this scenario is extremely time sensitive, and it might be very difficult to complete your objectives as well as identify the stone, especially if you are trying for a large amount of secrets. If you wanted to wait until scenario 3, your shrouds range from 1-4, but again, this delays the amount of scenarios you can use the Ancient Stone in, making the earliest possible use scenario 4 if you decide to wait.
Ok, so I hope I have established that it is very, very hard to get this item. So, is it worth it? I'm going to have to say probably not. Typically you only draw 1 card at a time, meaning you can only deal 1 damage at a time. Some combos with other seeker cards that draw, particularly Cryptic Research because it is Fast and therefore does not provoke attacks of opportunity. But Cryptic research is another 4 xp on top of what you have already spent. If you want a combat option for your Seeker, Strange Solution (acidic ichor) is probably better for damage on Normal or Easy mode where the chaos bag isnt too brutal, cheaper in terms of xp, easier to get, and doesnt take a hand slot. I've got a Plan! suffices for those who are stingy on XP. Those of us who play on hard salivate over testless damage, I know.... but most of your card draw will incur an AoO from any monsters you are engaged with, which you dont want to take. I'm really, really sad to say that this just isn't very good. 1.5/5 I really wanted more out of this.
Ancient Stone (Minds in Harmony): You can feel free to insert all the comments on the Knowledge of the Elders variant about how outrageous this is to get. So the only difference is the effect. So... this is just a sanity heal. Potentially it is rather a lot of sanity heal, so that's nice. It's also not nearly as annoying to activate, since you can drip heal your sanity over multiple turns when you draw your card for the round. Seekers probably dont really need this for themselves though, due to the extremely high amount of sanity soak allies and other cards like Logical Reasoning that they can play. Your friends will like you though. It's an okay support card. 2/5 Better, but still more trouble than it's worth.
Slip Away: The only card that does not cost XP in this pack. You add your Books to evasion, and if you win by 2 you can stop a non-elite from readying. A decent way to stall out a monster for a while, but I'm skeptical this is worth the 2 cost. 2/5 I doubt it.
Pay Day: Well, because this is rogue the chances you will get at least 4 resources off of this are pretty high. Yes, there are ways you can stack actions and theoretically make it ridiculous, but that probably wont happen most of the time. And you really have to ask yourself; is action comboing in this way really the best way for my rogue to make money? Probably not. Still, I think this is very playable if you get 4 resources out of it. 3/5 Seems ok.
Sacrifice: I love the flavor of this card, and it's effect could be pretty cool. There are lots of times when a mystic has stuff hanging around that they can't use, and maybe moreover its a nice way to eliminate Doom on a card that you have. You can sacrifice the Arcane Initiate or Alyssa or David Renfeld if the cost of keeping them around gets too high, and you can get a nice bonus while you're at it. 3.5/5 I like it, and sure to get better.
Crystalline Elder Sign: Ah yes, another Mystic relic that I am not going to use. As a mystic, the only stat that really matters to you is Willpower, that's the whole point of being a mystic in the first place. So why am I taking this, sealing a good token, and paying XP for it when I could just have a holy rosary? I'm not. 1/5 lame.
On Your Own: This is certainly the card in this pack that has me most excited. I think this is a fantastically thematic nice little card. The issue being that there arent that many survivor events that you are going to want to reduce by 2 cost all the time. Not enough to stack a deck with an make this worth giving up your chance at allies. I think this card is going to be very fun and special later down the line. But maybe not right now. 3/5 Investing for the future!!!!
As always, feel free to explain why you agree/disagree, and if you've played with any of these cards and how they worked out for you.