Orah, Skyclave Hierophant is another card that could be added to the Athreos mix, but it can also serve well as a commander in its own right.
It can be used alongside Taborax, as well as other new cards from Zendikar Rising, such as Angel of Destiny and Cleric of Life's Bond. All these creatures are synergistic.
Orah can also benefit from Edgewalker, which can reduce its mana cost to just two colorless, and of the rest of the cleric creatures that have similar mana bases.
Those are the best cards for commander in Zendikar Rising. For more Magic: The Gathering content, card lists, and guides, head over to our MtG hub page here.