There are four rarities of card in the game and you can tell a card's rarity from the colour of the gem in its centre. They run from Common (white) through to Rare (blue) to Epic (purple) and Legendary (orange).

The rarer a card is, the most is costs to create, up to a whopping 1600 for a Legendary. When you disenchant an existing card it's worth a paltry quarter of its build cost. Unless it's a golden version, that is, in which case you get its full value.

It's not obvious how to disenchant cards. If you go into "my collection" and tap on a particular card, there are buttons on the side of the display.

The top one, in red, shows the cost in dust to create the card, and the bottom, in green, tells you how much you get if you disenchant it. Press that to render one copy of the card into dust.

There's an easier way, though. At the top of the "my collection" display there's a "crafting" button. Press that and your collection will also show missing cards which you can tap on to create.

But, on the right, is a "mass disenchant" button. Using this will automatically turn all copies of anything you can't use into dust.

In practice, you'll want to use both. When you start out, and dust is in short supply, it can be worth disenchanting rarely used cards like Shieldbearer to make something more useful.

Mass disenchant treats gold copies of a card as different from the original, even though you can still only run two in a deck. So given their extra worth, new players often want to use individual disenchant to render those down too.