Ilverenna, Abjuratrix

Intimidate, haste, vigilance, first strike,
hexproof, flash
Whenever Ilverenna, Abjuratrix enters the battlefield, you may select target opponent's
instant or sorcery as it is being cast. Counter
that spell.
{x}{u}: Counter target opponent's spell, where X
is the spell's converted mana cost.
"All mystical threats are now accounted for!"