Dementor of Azkaban

Flying, vigilance, menace
Whenever Dementor of Azkaban attacks, reveal
the top card of your library. If that card's
converted mana cost is odd, you may cast it
without paying its mana cost. Otherwise, draw
a card.
Get too near a Dementor and every good feeling, every
happy memory will be sucked out of you.
—Remus Lupin