Umori, the Collector (231) [Ikoria: Lair of Behemoths Promos]

Companion — Each nonland card in your starting deck shares a card type. (If this card is your chosen companion, you may put it into your hand from outside the game for {3} as a sorcery.) As Umori enters, choose a card type. Spells you cast of the chosen type cost {1} less to cast.