In Loop Hero the Crono Crystals card is a terrain card that doubles the effect of adjacent tiles, causing them to double their production each day. You will not be able to get the Crono Crystals card until the fifth round of your loops but once you have it you can exploit it to spawn a lot of enemies to quickly fill the Boss Meter in the top-left corner. The benefit of this is it will make the bosses spawn considerably quicker which will mean they will have less HP and damage making them a lot easier to defeat. Another way to take advantage of the Crono Crystal card is to use it to double the equipment you gain per loop by placing the card next to an enemy spawn such as a Vampire Mansion, Blood Grove, Cemetery, Spider Cocoon or Battlefield which will double the spawn of enemies in the loop for the adjacent spawns.
The Crono Crystals card is without doubt the best terrain card in Loop Hero with its ability to double the effect of adjacent cards. This means it is important that you place it wisely and always look to build around it to exploit it as much as possible. When the Chrono Crystals card is placed near a Meadows card it will provide 4 HP per day, this can also be done with the Blooming Meadows card where it will provide 6 HP per day. By placing the Treasury card somewhere near to a Chrono Crystals card you can double the amount of treasure and loot you earn. These are just some of the many ways in which you can exploit this card.
Take a look at our Best Card Combos guide to find out how you can use the cards in your deck to farm more resources and acquire better gear.