Urza's Incubator

As Urza's Incubator enters, choose a creature type.
Creature spells of the chosen type cost {2} less to cast.

Sethron, Hurloon General

Whenever Sethron, Hurloon General or another nontoken Minotaur you control enters, create a 2/3 red Minotaur creature token.
{2}{B/R}: Minotaurs you control get +1/+0 and gain menace and haste until end of turn. ({B/R} can be paid with either {B} or {R}.)

Heartless Summoning

Creature spells you cast cost {2} less to cast.
Creatures you control get -1/-1.