Miyala, the Twin-Souled

Miyala, the Twin-Souled can't be blocked.
Whenever you cast a spell, if you paid mana for
it, you may cast a card that costs less and shares a
card type with that spell from your hand without
paying its mana cost.
Whenever Miyala attacks, manifest the top card
of your library. The manifested card enters the
battlefield tapped and attacking.