Unesh, Criosphinx Sovereign

Flying
Sphinx spells you cast cost {2} less to cast.
Whenever Unesh, Criosphinx Sovereign or another Sphinx you control enters, reveal the top four cards of your library. An opponent separates those cards into two piles. Put one pile into your hand and the other into your graveyard.

Amonkhet Remastered

Flying
Sphinx spells you cast cost {2} less to cast.
Whenever Unesh, Criosphinx Sovereign or another Sphinx enters the battlefield under your control, reveal the top four cards of your library. An opponent separates those cards into two piles. Put one pile into your hand and the other into your graveyard.

Hour of Devastation

Hour of Devastation Promos

A pile can have no cards in it. In this case, you'll choose whether to put all the revealed cards into your hand or into your graveyard.

In multiplayer games, you choose an opponent to separate the cards when the ability resolves. This doesn't target that opponent. Because the cards are revealed, all players may see the cards and offer opinions.

To determine the total cost of a Sphinx spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions. The mana value of the creature remains unchanged, no matter what the total cost to cast it was.

Unesh's cost-reduction ability doesn't reduce the cost to cast itself.

You (not your opponent) choose which pile to put into your hand and which to put into your graveyard.