The Ur-Sphinx (Extended Art) | (097) [Commander: Reality Fracture]

Eminence — As long as The Ur-Sphinx is in the command zone or on the battlefield, other Sphinx spells you cast cost 1 less to cast.

Flying

Whenever one or more Sphinxes you control attack, each player mills that many cards. For each player, you may cast a card that player milled this way without paying its mana cost.