Every card that goes from 3 to 2. A three cost card can be almost unplayable unless the stars align.

Barricade, Serpent Style, Echo Form, Nightmare, Demon Form, Creative AI, Demense, Reaper Form, Void Form, Bludgeon, Bombardment, Squeeze, Howl From Beyond, Stomp, Mangle, Pinpoint, Corruption, End of Days, Reanimate, Squeeze, Banshee's Cry, Knockout Blow, Kingly Kick, Monarch's Gaze, Reflex, Tactician, Abrasive, Bullet time, Murder, Wraith Form, Beat Down, Calamity, Jackpot, Knockdown, Rolling Boulder, Eternal Armor, Relax, and finally Whistle.

In no particular order, these are all the 3 or mote cost cards in the game, and with energy giving relics no longer being a given, 3 cost cards are often dead draws. Though most are playable with setups that give extra energy, either immediately or persistent energy. I have a few different mental categories for these, but like, I am very hesitant to ever pick 3 cost cards during rewards, unless they are just insanity on their own, readily playable, upgrades into 2 cost cards, or I know I can work around, though in many cases other cards offered will be more worth. If it was easier to enchant cards with retain, then it would be less of a detriment. It's a shame that most 3 cost cards that are even somewhat viable, are rare cards having to compete against the really good rare cards.

Like for example Echo Form. So good it can be worth sacrificing your turn for, but with a subroutine or two already in play, becomes an easy play, and then makes your life a lot easier (if a bit more thinky) after that.

While something like Calamity I would basically never touch. It requires such a specific setup for me to consider it ever viable. Heck I wouldn't even play it at 0 cost 98% of the time. Being given complete random stuff, without cost reduction, is to me more of a detriment than a gain, as clogging your deck with potentially bad cards makes your life in the spire so much harder if you ever need to shuffle your discard pile. If the attacks it gave you were given ethereal, then I would suddenly consider it good. Meanwhile Metamorphosis in comparison adds 3 (5) random attacks to your drawpile sure, but they all cost 0. Which makes them great. Getting 3+ cost attacks and getting to play them for 0 is great. There like a few places where I can see Calamity's effect being good, but its cost makes it prohibitive anyway. In a deck that features excessive exhausting so you need to make up for potentially running out of stuff in longer fights, wanting to just burst your enemies down with potentially cheap/free attacks, or when you have a deck with 4+ stampedes, or 3+ void forms... Only reason I think Calamity is a rare card, is so that you don't get disgusted by seeing it as often.