Lex's Plans

When Lex's Plans enters the battlefield, look at
the top 20 cards of your library. Exile 3 cards
with plot counters on them. Place all cards not
exiled this way on the bottom of your library in a random order.
Whenever you would be delt combat damage, if
there are one or more exiled cards with plot
counters on them, randomly place one in your
hand and prevent all combat damage that would
be delt to you this turn.