Quizzy, Question King

When Quizzy enters the battlefield,
target opponent discards half the cards
in their hand, rounded down.
Whenever Quizzy attacks, defending player mills
half their library, rounded down.
When Quizzy dies, target opponent sacrifices
half the nonland permanents they control,
rounded down.
Legend has it that there's never been a question
Quizzy couldn't answer!