Like regular decks, except cannot be equipped, cannot hold any regular spells, but can hold a ton of TC (like 100).
These decks should be purchasable from vendors via gold, perhaps 50k gold, as well as dropped from bosses, and be auctionable (ie Bazaar) as well.
I'm sure many people would love to be able to hoard a bunch of TC into a single deck.
Another idea (in addition to, not an alternate idea) is to create TC vaults that can hold any kind of TC, including gardening and castle magic TC, with a limit of perhaps 250 each, and should be able to give a custom name to the TC vaults. Names like the different magic schools, gardening, and magic, where the name would become "TC Vault: Gardening" for example.
I like this post because it is an original idea that I feel would be very much appreciated by the community. I myself often find myself in the position where I am at max gold and max tc. At this point you have two options, you can just give up and let your gold be thrown into the void, or you can trash your empowers that you have bought in the past with your max gold. If you could place those in a vault ether crafted or crown bought that would be a much better option. Another idea I share with much of the community is treasure cards in your bank and shared bank. This would just be a much better quality of life feature that would be highly appreciated by the community
When you click on a treasure card, it brings up a large 'copy' of it on the left side of the window, then you have to press the (+) button to bring up the little pop-up to choose how many you want to move to the vault. Double clicking doesn't seem to do anything either. Was hoping it would be treated just like a regular spell deck, where you click on a TC and it moves it automatically. Hope they change the way it works, because it's a bit annoying at the moment.
Also, you have to buy it, can't craft it (not yet anyways).