Dr. Bolivar Trask

When Dr. Bolivar Trask enters the battlefield, reveal the top 4 cards of your library. Put all Sentinel cards revealed this way into your hand, and the rest on the bottom of your library in any order.
Sentinel spells and activated abilities cost you {1} less to cast and activate.
"Soon my Sentinels will take flight...to keep the world and the human race safe forever."