The Black Goo

Replaces Morophon, the Boundless.

Changeling (This card is every creature type.)

As The Black Goo enters, choose a creature type.
Spells of the chosen type you cast cost {w}{u}{b}{r}{g} less to cast. This effect reduces only the amount of colored mana you pay.

Other creatures you control of the chosen type get +1/+1.