Ambriel, Divine Coherence

Flash

Prowess (Whenever you cast a noncreature
spell, this creature gets +1/+1 until end of turn.)

Whenever you cast an instant or sorcery spell, you
may return another target instant or sorcery card
with lesser mana value from your graveyard to your hand. If you do, flip a coin. If you win the flip, you may cast that card without paying its mana cost.