Ileana, the Avid Genius

Flash
Whenever a spell is countered, exile it until Ileana leaves the battlefield, and put two +1/+1 counters on Ileana.
Remove two +1/+1 counters from Ileana: cast a noncreature card exiled by Ileana. Spells cast this way cost {1} less.
"So many useful things are just thrown away, so
much potential."