Lexi's Determination

(You may cast a Battlegroup from your hand only if
you dealt combat damage on your previous turn. If
you do, cast it as if it were an instant)
You may sacrifice two creatures or one land
instead of paying this card's casting cost.
Discard a card from your hand, then look at the
top 8 cards of your library. Put one of them into
your hand and shuffle the rest into your library.