The Behemoth Slayers

Ferocious — If you control 4 creatures with power
4 or greater, The Behemoth Slayers gain trample.
Whenever The Behemoth Slayers attack, you may sacrifice another creature with power 4 or
greater. If you do, put a +1/+1 counter on The Behemoth Slayers, then double the number of counters on them.