Merciless Inspection

Black creatures get +1/+1.
Non-black creatures get -1/-1.
"Those who make it into the armor of the Armies of
Darkness have had their craft drilled into them.
Their discipline tried in battle and fire. Their
loyalty tested in blood and their mercy honed
away. Pray if you ever meet them it is their
worst day and your best. If it is the other way,
you've no chance."