Jei, Mox Unbound

{t}: Add {u} to your mana pool. Spend this mana
only to cast a spell or activate an ability that
targets one or more spells an opponent controls.
Whenever Jei becomes the target of an
enchantment spell, sacrifice it.
"After all these years... I have finally found it.
Another one of our great lost artifacts that overflows
with antimagic, ready to be strung together."