The Three Great Aurochs

Trample
Whenever an Auroch enters the battlefield under
your control, create a 3/3 green Auroch creature
token with Trample and Haste.
Whenever an Auroch you control attacks, you get
a Stampede counter, then Aurochs you control
get +X/+X until end of turn, where X is the
number of Stampede counters you have.