Tu-Ket, Aspiring Sphinx

Whenever Tu-Ket, Aspiring Sphinx enters the graveyard from anywhere, target a player, that player chooses to either;
•Discard 1 card.
•Mill the top 4 cards of their library.
If cards were milled with the effect of Tu-Ket, Aspiring Sphinx, all players may play those cards until the next end phase.