Trading Cards are one of the most unique features of the Acid Mines.

Command: /cards

You can get booster packs from TH or through donating.
Open booster packs with /cards open

You can store all of your cards safely by using /cards storage

Each card has a rarity of either Common, Uncommon, Rare or Ultra. (also Promo).
Each card is part of a series from 1-12. Instead of having cards numbered from 1 to 2000+ they are numbered within their series.
So you might have series 1 #53 and series 2 #53 and they are completely different cards.

The reason for having 12 series of cards is for distribution. 
Cards will appear in your inventory randomly when you train skills. Gaining XP in any skill has a chance to grant a card (some skills are better than others).
The possible cards that you can obtain cycles each week. On week 1, you will only find series 1 cards. On Sunday it will switch to series 2 for the next week, and so on.
Cards change every Sunday. After 12 weeks it will cycle back to series 1 again.

Each of the 12 series contains 5 ultra cards, 10 rare, 25 uncommon and roughly 70 commons. (These numbers will change as cards are added)