Khemos's Authority

Target player reveals their hand. You choose a
nonland card from it. That player discards that
card.
Supremacy - Whenever an opponent casts a spell
or activates an ability while this spell is on the
stack, put Khemos's Authority from the stack
onto the battlefield transformed.
Lay bare your mind to Khemos, hoarder of knowledge,
so that he may bring unto you the bliss of ignorance.