This is achieved in Kaycee's Mod.
Stand up and turn around. See the painting on the right hand that has a combination of cards displayed on a playing field? You have to obtain those cards and play them during a match against Leshy. This will unlock an item that can be collected by interacting with the painting. The cards must match the position they are shown in the painting. You have to do this three times and unlock all the items to get the achievement
Items list may contain spoilers.
Items:
*** Spoiler - click to reveal ***1. Magick Paint - This will allow you to erase all the abilities from the enemies frontline cards. This item can be used to erase all the abilities on the Moon card at the end of the challenge run. Doing so will allow you to use flying cards to attack Leshy directly and defeating him without destroying the Moon card. This unlocks another achievement, Bad Moon. The only other way to get Bad Moon is to pull your teeth using pliers, but you need a card that replenishes items indefinitely so you can keep doing it.
2. Sturdy Watch - This will allow you to rotate all the cards clockwise (your cards move left-to-right, and Leshy's cards move Right-to-Left; cards on the edges switch teams, up and down respectively)
3. Magnifying Glass - This will allow you to search your deck for a card and put it in your hand
Note: When you place the cards, the screen will shake. After the battle go and collect the item and then sit back down. The item will be added to your item inventory on the right hand side and can be used in the next battle.