Nightingale, Sly Observer

Flying, Deathtouch
At the beginning of your upkeep, choose a player;
you may look at the top card of their library this turn.
Whenever one or more creatures you control deal combat damage to a player,
exile the top card of that player's library.
You may cast spells exiled with Nightingale by paying life
equal to their mana value.
If a player has 15 or less life, Nightingale has lifelink.