Veronica, Eternal Rose

Deathtouch, first strike
Creatures you control have undying. (When it dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)
{t}, Sacrifice three creatures: Search your library for a card. You may cast thar card without paying it mana cost, otherwise put that card into your hand. Then shuffle your library.