Endeavors in ESO reward you with a new currency called Seals of Endeavor. The amount varies based on the day and challenge level of the Endeavors themselves. They are account wide, have no collection limit and can be accessed from the Crown Store menu. With these seals you can purchase from the Seals of Endeavor section of the crown store.
In order to find the Seals of Endeavor section, open the Crown Store and choose in the upper right hand corner the second symbol from the left. The seal value for individual Crown Crate items differs, which might require saving up for the most valued items, such as Radiant Apex mounts.
Since we track the ESO Endeavors manually, update times can vary.