Gold cards are gold-versions of existing cards and are introduced at the end of Season 1 (April 30, 2019). Cards of all rarities have Gold versions.
Gold cards and regular cards
Gold cards have exactly the same stats as their non-gold counterparts - they are much rarer though and look different.
A Gold version (work in progress) and the standard version of an Elite card
Gold cards behave on the battle field the same as regular cards.
How to get Gold cards
There exist three ways how to get Gold cards:
1. Opening card packs
2. Receiving a seasonal reward
3. Bonus reward from winning a Draft
Whenever you open a card pack, you have a slight chance that instead of the regular variant of the card, you will receive a Gold card of the same card. This stacks with the rarity of the cards - while it is already rare that you get a Standard Gold card, it is extremely rare that you get an Elite Gold card.
Gold cards are also part of the seasonal rewards.
There is also a chance that one of the bonus rewards from winning a Draft will give you Gold card.
It is not possible to create Gold cards from resources.
Article: Creating cards