The Ur-Sphinx

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

EDHREC rank #15922

USD reference: $5.92 (~₱370.57)