The Ivory Giant

Convoke (Your creatures can help cast this spell.
Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)

Trample, reach

Whenever The Ivory Giant enters or attacks, cause
a Stampede. (Creatures you control with the same color of this card gain +3/+3 and trample until end
of the turn, untap those creatures.)