The Joker, Who Laughs Last

You may look at the top card of your library any time.
As long as you have no cards in hand, you may play lands and cast spells from the top of your library.
{r}, Discard a card: Tap The Joker, Who Laughs Last. It gains indestructible until end of turn and deals 1 damage to any target chosen at random.
{u}, {t}, Discard your hand: Counter target spell unless its controller discards their hand.