Osos, Banished Alchemist

When Osos, Banished Alchemist enters the battlefield, choose a nonland card type.
Spells you cast of the chosen card type cost {1} less to cast.
Once during each of your turns, you may cast
a card of the chosen type from your graveyard.
If an instant or sorcery spell is cast this way,
exile it instead of putting it anywhere else.