All Cost 0 and are action/ruins unless otherwise noted. I've designed them all to resemble another card and to be largely useless in most situations. They're not all meant to be equally bad (and some may be strictly better than others), but they're all meant to be bad.
Abandoned Feast: Trash this. Gain a card costing up to 2 and a ruins
Ruined Chapel: Trash a card from your hand that isn't a Treasure, a Victory Card, a Shelter or a Ruins
Ruined Council Room: +2 cards, each other player draws a card
Ruined Lab: +1 card, +1 action, discard an action card
Throne Ruin: Play an action card twice, then trash it. Gain a ruins.
Ruined Cellar: Discard any number of actions or treasures from your hand. For each card you discarded, +1 card
Ruined Workshop: Gain a card that isn't an action or treasure costing up to 2. Put it on top of your deck
Ruined Moat (Action/Reaction/Ruins): Trash this card, gain a ruins. Reveal and discard to prevent an attack. If you do, gain a ruins.
Ruined Courtyard: +1 card. Put a card from your hand on top of your deck.
Once Great Hall: (Action/Victory/Ruins) +1 action. Worth 0VP
Broken Bridge: +$2. Each card costs $1 more
Ruined Ironworks: Gain a card costing 0. If it's a treasure, $1. If it's an action, +1 action. If it's a curse, +2 cards
Ruined Lighthouse (Action/Duration/Ruins): +1 action. At the start of your next turn +$1, gain a ruins. While this is in play, attacks have no effect.
Shipwreck: +$2. Each player may put a card from their hand on top of their deck (you must). Each other player may trash a treasure.
Ruined Treasury: +$1. Immediately put this card on top of your deck.
Ruined Wharf (Action/Duration/Ruins): +1 card. At the start of your next turn, +1 buy, discard down to 4 cards in hand.
Ruiniversity: +2 actions. Gain a ruins
Ruined Watchtower: Draw until you have 4 cards in hand
Desecrated Monument: -1VP. +$2.
Ruined Mint: Trash a card that isn't a ruins. Gain a copper
Robbed Vault: Discard any number of cards from your hand. For each treasure you discarded, +$1.
Ruined Counting House: Gain a copper; put it in your hand.
Ruined Stables: Discard a treasure. If you do, +2 cards.