Well I also hope others join in, but for now you'll have to make do with me
Peace Offering: really nasty Red Coin strats are emerging just looking at this card. It's creative for sure but not really healthy, you know. I can't simulate all the mindgames around it of course but knowing it exists means you're going to be playing very weirdly if you're on Blue coin against ST, knowing they can just yeet your TA'd unit back into the deck, or clog it with the Lamp Djinn, or play a high-provision unit that has a great deploy effect then use Peace Offering to put it back and at the same time put back your high-provision unit that might be an engine or an Yghern or something of the sort. I don't think it's too strong or too weak, just wrong as a concept imo
Librarian of the Dead: I don't think putting cards back into the deck happens often enough for a 1 damage random ping from a 7 provision zero tempo card to be worth it. Aside from the bad stat line, I'd say these kinds of Artifacts are a slippery slope, due to their uninteractivity. I don't like this one either to be honest.
Riordan: a better Iorveth, and not the "a little more prov-efficient" kind of better, but the "it's busted by comparison" kind of better. Playing multiple Serpent Traps and Pitfall Traps. I don't know if it's strong or weak, maybe Iorveth should be changed to this? I'd say it's broken but we've seen more broken-sounding concepts make it to the final game so it's possible.
Ciaran: hmm I'm not sure what his purpose is. You play him, he gets removed by generic 4 damage removal, and now he's on the top of your deck... well, what did you really accomplish? The thing you wanted to protect has no protection still. You traded 9 provisions with a 4 provision removal and didn't really do anything. By the way, all the ideas for the Defenders are very neat but I think the concept of Defender is one that shouldn't be tinkered with too much. All factions have one that's more or less the same, and that's how it should be or you risk enabling strategies that aren't really fun for the other guy
A Spider's Folly: I don't think you fully grasped what Ambush and Spring means. Ambush means the card flips over on its own because of a condition that has been met, Spring means the player clicked it. If your trap is going to have the Spring tag it should have a worse effect, here's how I'd reword this card.
Ambush: When an opponent's unit is moved, spawn 2 Elven Deadeyes and destroy self
Spring: spawn 1 Elven Deadeye and destroy self
I added another Deadeye to the ambush part otherwise the card is unplayable due to bad cost, but anyways I hope you get the whole Spring thing now
Oh wait. Just as I was going to the next card, I noticed your elven deadeye is different. Ah well that changes things. Why'd you use the same name? Haha, anyways he's an artifact himself? And he periodically switches between Spider's Folly? I'm not sure if I'm following exactly but this sounds like some Uninteractive bs going on and I don't think that's great for the game
Angus: that melee effect looks really interesting, and I'm not talking specifically about traps but just having someone deal damage according to a unit's provision cost in the graveyard. Personally I think the provs and body need to be changed, right now it seems too strong.
I'm not following the difference between gold deadeye and bronze deadeye, but I magine a 4 tempo play that transforms something into a tiny artifact engine isn't as good as 4 body with potentially 7 damage
Iorveth: very acceptable design. I'm not too fond of the cards it spawns, especially that one bronze decoy but it's alright. If ST had something like this that spawned Rebukes they'd be the happiest players around lol
Milaen: not very interesting, I'll be honest. Just points and numbers, not really an ability worth adding to the game, I feel. But then again I'm not a fan of movement decks in general so I'm probably biased, maybe it's amazingly creative
Scoia'tael Commando: "jumble" made me chuckle, heh, I don't think this is a good card though, nor do I think jumble is a good effect if it does what I think it does (change the cards around in a row randomly). It'll proc melee'd sentinels I guess, in which case that's huuuuge damage, even better than a Gaetan possibly so eh, not a big fan of this card. But maybe that's not what jumble does.
Web Trap: here we have an evolving artifact that randomly locks, seizes, and bleeds. The only non-insane thing about this card is the "if opponent has X number of cards on the board" condition which is interesting, sort of like an Adrenaline for the board.
Etriel and Muirlega: play an artifact with 6 power? Artifacts don't have power, maybe you meant provisions. In any case, these look nice. One's a tutor, the other's an offensive consume. Big think here, I can't say I'd be upset if these were in the game but I also don't think it's necessary for these mechanics to be tied to a Duo. They could work just as fine as separate cards, tweaked to make up for the lost "sibling" card.
Wild-Snipe Chase: this whole wardancer thing has way too many moving parts I feel, not to mention it's supposed to be a thinning card that gets summoned from the deck, yet so many cards spawn it and play it. I don't get it
As an overall suggestion I would say to avoid using already-existing names and pictures for cards that do completely different things. I think it's reasaonable for me to assume you're talking about the token when I read "Elven Deadeye" and see the image of the in-game Elven Deadeye. The tiny golden border isn't enough lol