Hedric's Promise

(You may cast a legendary sorcery only if you
control a legendary creature or planeswalker)
X target creatures you don't control can't block
until the beginning of their controllers
next upkeep. If X is 10 or more, there is an
additional main and upkeep phase this turn,
untap up to 5 lands you control.
Exile Hedric's Promise.
"This war will be over by the full moon, one way
or another." - Hedric, Master Tactician of Duvin