With the patch on July 12, 2018 cards were added to the game that do not exist in paper Magic. The only exception to this is Serra Angel which is a reprint from other sets e.g. Dominaria.
The cards are not following any specific theme or mechanic and are part of the NPE (New Player Experience). They can be crafted with Wildcards and are Standard-legal. They are not included in Packs and therefore won't appear in Draft.
A list of cards can be found here, a card gallery here.