Lydia Frye
{2}{U/B}Legendary Creature — Human Assassin
Lydia Frye can't be blocked by creatures with power 3 or greater. At the beginning of your end step, surveil X, where X is the number of tapped Assassins you control. (Look at the top X cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)