Alexia, Doom Blade Incarnate

Partner with Fyfnar, Flaming Mace
When Alexia, Doom Blade Incarnate enters the
battlefield, destroy half X creatures. If you do,
search all libraries and graveyards cards named
Doom Blade and exile them. They gain "You
may cast this spell from exile only by removing
twenty counters of any one type from a creature.
If there are no cards named Doom Blade in exile
as this spell resolves, you win the game."
{x}, {t}: Destroy target nonland permanent
with mana value X.