Astolfo, Rider of Black

Changeling (This card is every creature type.)
As Astolfo, Rider of Black enters the
battlefield, 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.