Liliana's Sacrifice

As an additional cost to cast this spell, sacrifice
any number of creatures or planeswalkers.
Destroy up to X target creatures, where X is the
number of creatures and planeswalkers sacrificed
while paying for this spell. If you control a
Gideon planeswalker, add one loyalty counter
to it.
Liliana's sacrifice bought Gideon and the others time
to retreat.