Despite the obvious disclaimer that cards are good/bad depending on matchup and deck, what are the very best and worst cards you have encountered? I'll start:

Best card in the game, in my opinion:

Witch of the wilds!

For the uneducated: Witch of the wilds is a 4-power Untamed creature that allows you to play a single untamed card in rounds where you play your other factions. This card is incredible.

A : This lets you play powerful untamed cards that typically function as combo pieces in the untamed faction, for example playing Full moon or Hunting Witch before filling the table with minions, comboing with Stampede or Scout or Regenerating a minion from the active faction, Witch of the wilds turns these cards that are often limited in usefulness into dramatically larger toolbox effects.
B : Playing non-combos for their benefit and to just empty your hand and draw more, for example Nocturnal maneuver or Cooperative hunting.

C : Play a minion or artifact to then use in an untamed round later!

Worst card in the game, in my opinion:

Bad penny. Booo!

This would be a terrific MTG or HS minion, infinite self replacement? YES! This is a TERRIBLE Keyforge minion.

A: She's a monolateral combo piece. A 1 power minion with no other abilities has NO use on it's own. She cannot kill stuff and reaps ember no better than anybody else. If you have cards that combo with a regenerating 1 power minion then sure, do your Pawn sacrifice combo or kill her with Seeker Needle for a bit of ember, keep in mind that these other combo cards can still do their thing without bad penny (killing urchins, damaged minions, enemy minions) but Bad Penny isn't useful without these other cards to combo with, a monolateral combo piece is a BAD combo piece.

B: She regenerates by going back to your hand, this means that until you play shadows again she starts killing card-draw windows by just being there, in your hand. Filtering and dumping your hand is good in Keyforge, and she just sits there, killing card draw after card draw, god help you if you have 2 Bad Pennies. Most often you're better served discarding Bad Penny then actually playing her. She'dd be better if she Purged herself after being destroyed.... Heck she'dd be great if she purged herself, it'd even be more thematic for her name!

I've never seen a deck with bad penny that wouldnt be better served by an Urchin....

Bad Penny + seeker needle.

24 minutes ago, tsuruki said:

Worst card in the game, in my opinion:

Bad penny. Booo!

I think Dextre is worse for similar reasons.

1 hour ago, twinstarbmc said:

I think Dextre is worse for similar reasons.

But his capture hability is useful.

3 hours ago, twinstarbmc said:

I think Dextre is worse for similar reasons.

I agree that Dextre is bad in a similar way, but a fight stat of 3 and the capture mechanic basically boils down to him trading with weak creatures / slowing down the game clock by 3 enemy ember / putting strong enemy critters in killing reach, he doesnt have the same combo potential as bad penny, so that's wrose, but at least he actually does affect gameplay by himself a bit. Also he's a member of the most draw-heavy faction so that remedies his disadvantage a bit.

Worst Cards:

I would add Sacrificial Alter, because many do not seem to have 'human' cards.

I would also add biomatrix backup given the recent resolution.

Epic Quest seem too difficult.

And Whispering Reliquary never excited me.

Best Cards:

Bait and switch - its one of the best cards to punish an opponent with too much amber.

Shadow Self - Most power creatures are the weakest and tend to get killed. Taunt does not protect against direct damage, but this does.

Arise - Nothing like getting a giant hand of creatures to play from your discard.

Mimic - Its very versatile and very good.

I think its hard in this game.

What was the resolution with Biomatrix Backup?

Epic Quest is actually pretty... epic.

25 minutes ago, Mud Turkey 13 said:

What was the resolution with Biomatrix Backup?

P4: "The player taking a turn is referred to as the active player. The active player is the only player that can perform actions or make decisions; a player does not make any decisions when it is not their turn."

Now, because Biomatrix says you "may" archive the creature, during turns where your opponent is active player he can just chose then not to have the Biomatrix effect trigger.

Best: Key Charge: Play: Lose 1[A]. If you do, you may forge a key at current cost.

it is way too easy for Untamed to get 7 Amber.

Worst: Key Abduction: Play: Return each Mars creature to its owners hand. Then, you may forge a key at +9[A] current cost reduced by 1[A] for each card in your hand.

Playing this first with no Mars creatures will cost you 10 Amber. No Mars creature has a good play effect, and several of them have bad ones. If you started with 6 Amber, you would have forged. Playing a card for 1 Amber increase the cost by the same amount. Mars has very few 2+ Amber cards that don't hurt this card in some way. This all means that this card only works with very specific other combos pieces, or if you have 3 or more Mars creatures on the board from earlier turns that your opponent was nice enough not to kill, and you started the turn with a good amount of Amber, and replaying those creatures isn't going to hurt more than it helps (or it is the final key). Keeping in mind that deck lists are public information, so your opponent will be looking for this.

2 hours ago, Revert said:

Best: Key Charge: Play: Lose 1[A]. If you do, you may forge a key at current cost.

it is way too easy for Untamed to get 7 Amber.

Worst: Key Abduction: Play: Return each Mars creature to its owners hand. Then, you may forge a key at +9[A] current cost reduced by 1[A] for each card in your hand.

Playing this first with no Mars creatures will cost you 10 Amber. No Mars creature has a good play effect, and several of them have bad ones. If you started with 6 Amber, you would have forged. Playing a card for 1 Amber increase the cost by the same amount. Mars has very few 2+ Amber cards that don't hurt this card in some way. This all means that this card only works with very specific other combos pieces, or if you have 3 or more Mars creatures on the board from earlier turns that your opponent was nice enough not to kill, and you started the turn with a good amount of Amber, and replaying those creatures isn't going to hurt more than it helps (or it is the final key). Keeping in mind that deck lists are public information, so your opponent will be looking for this.

Key Charge can't be the best card, because there is a creature with the same effect.

The good:

The Harder They Come (Sanctum, Action) - Play: Purge a creature with power 5 or higher.

Skippy Timehog (Logos, Creature) - Play: Your opponent cannot use any cards next turn (cards can still be played and discarded).

Collar of Subordination (Dis, Upgrade) - You control this creature.

Treasure Map (Shadows, Action) - Play: If you have not played any other cards this turn, gain 3 amber. For the remainder of the turn, you cannot play cards.

Earthshaker (Brobnar, Creature) - Play: Destroy each creature with power 3 or lower.

Martians Make Bad Allies (Mars, Action) - Play: Reveal your hand. Purge each revealed non-Mars creature and gain 1 amber for each card purged this way.

For the ones that might not be obviously self-evident; I like the Treasure Map because it’s such a strong turn 1 play if you’re going first. Martians Make Bad Allies is also fantastic for the potential for speeding up your deck.

It's really hard to say honestly, there are some cards I have in multiple decks that are mostly terrible in one but great in another simply do to how they interact with the other cards. That said if I had to break them down just on their individual effects:
Good:
-Bait and Switch: Played at the right time it's a game changer, have gone from 0 to 5 all while my opponent went from 9 to 5 in a single turn without using any other cards.
-Library Access: Even if I don't have any great logos combos being able to field them all and thin out the deck is amazing. Without a board wipe I usually gain quite a bit of control out of this card.
-Mother: Always nice to have that extra card draw potential.
-Phoenix Heart: Let's me suicide a character, bring them back, all after dealing 3 damage to everything on the board? It's not exactly a board clearer but for no chains and returning a potentially good creature it's very nice.
-Sample Collection: Just an absolutely amazing card, being able to just outright remove opponents creatures from their list of options especially in large numbers is never not good.

Bad:
-Soul Snatcher: While it can get me quite a bit of aember it rarely gives my opponent any less if not more if I'm doing well. I suppose it will run well against sanctum but I don't tend to see myself fighting them often.
-Key Abudction: It's rarely if ever worth it, I don't have any heavy mars decks and even if I did most mars creatures don't seem to have good "play" effects making this usually a bad choice except in very specific circumstances.

8 hours ago, Ignithas said:

Key Charge can't be  the best  card, because there is a creature with the same effect.

Untamed has better recursion with actions than creatures.

Good,

I would say Succubus is top teir. My friend has a deck with three!! of them, and it stalls the heck out of every deck I have. Further more, I would suggest that a card that lowers hand size is worth more than an identical one that raises hand size as a general rule. Worse, with my friends deck, if I somehow end up with a deck with 13 or more chains at any point ( from Tournaments, etc) then I have a scenario where I could draw up to a hand size of zero.

Bad,

I would say Sacrifical Altar, because of it being a fully dead card if there are no humans.

6 hours ago, Revert said:

Untamed has better recursion with actions than creatures.

Chota Hazri is a Untamed card.

Bad penny is incredible combined with pawn sacrifice or seeker needle, etc I have a deck with a bad penny and two pawn sacs. It's amazing.

My vote for worst card would be Truebaru. (7 power, You must lose 3 Æmber in order to play Truebaru. Taunt. Destroyed: Gain 5 Æmber.)

There’s so much non-destroyed removal in the game (return to hand, purge, shuffle into deck, etc.) that the effect of playing Truebaru can easily just be “lose 3 Æmber” and it’s better to discard it.

Bad Penny + Hunting Witch + Auto cannon is very good situation to have bad penny in.

My friend master planned Hunting witch just to do this to me it was amazing.

On 11/21/2018 at 10:27 AM, Revert said:

Untamed has better recursion with actions than creatures.

Untamed has amazing Creature Recursion

Not counting Seed and Eye, since it does both, you still have World Tree and Regrowth

And nature's call. Chota Hazri is the most powerful card for me but only in context. The context being that it enables I believe the only opening turn win combo possibility in the game. One of the great things about this game is that everything has counters and relies on other things to work and everything has uses even ostensibly poor cards like Penny.

Worst things for me are big buff critters with no other effects like Valdr. All they do is reap. Woo.

The single best card, without too closely considering the rest of the deck, synergies with other cards, or what your opponent is playing is Arise! 1 Chain to bring an entire house worth of creatures into your hand is absurdly cheap and could tip the tide and completely lock out your opponent from play.

After playing many games I can say that the absolute best card in the game is Nepenthe Seed .

Its versatile. Its good in any deck. Its a combo maker. It has no chains. Its Nepenthe Seed .

Since no one has mentioned this card yet, I feel one of the best cards is Library Access. Leads to some blowout turns...

Library Access is terrible! Everytime I play it, I draw nothing but out-of-house cards I can't use and would have drawn at the end of my turn anyway! I have drawn exactly ONE card I could actually use with Library access in about twenty games! I think the luck gods hate me. : - )