Rinaldo, King's Slanderer

When Rinaldo, King's Slanderer enters the
battlefield, put a +1/+1 counter on each other
creature you control. Whenever Rinaldo,
King's Slanderer attacks alone, sacrifice it at
the end of combat.

“Berates Conan as a ‘black-haired barbarian’”
— R. E. Howard, “Phoenix on the Sword”