Spirit Orbs are the primary method of obtaining new cards in Duelyst. Each Spirit Orb contains 5 cards. At least 1 card will be RARE or better. They can be purchased in the Armory, obtained as rewards from The Gauntlet, or be awarded for completing an Achievement.
To Open a Spirit Orb, click on the "Spirit Orbs" link in the lower left of the screen. Once inside, you can view your acquired orbs and open them by simply dragging orbs to the center of the screen.
Spirit Orbs from the Rise of the Bloodborn and Ancient Bonds sets operate a little differently in that they will give you three copies of three different cards from the set. However, once you have unlocked those cards, you will not receive additional copies of the cards as you might from other sets. Due to this, you cannot disenchant or craft cards from these sets.