For Magic's Dissension set, Okera illustrated the Azorius Æthermage card for Wizards of the Coast.
You can view Azorius Æthermage here: http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=111256Unlisted Artists
Note that the gatherer database does not usually show promotional cards. The gatherer can also experience difficulties with links like this. If you are taken to an error page, input "Azorius Æthermage" into the search bar, and you should arrive at the page linked above. If Okera ever illustrates more Magic: the Gathering cards, you can view them by clicking the artist's name on the linked page.