The lich slams his fist onto his writing desk, snapping it in half. He roars, and yells BRING OUT A BEHEMOTH. MAKE THEM BURN AND PUT THEIR HEADS ON A PIKE!
The lich watches as a huge monster made of the half-decayed bodies of assorted races rose from the bowels of the cave, and says PROVE TO ME THAT YOU HAVE SUCCEEDED IN KILLING THE OFFENDERS AND YOU WILL EARN YOUR FREEDOM
The bodies groan in unison and the creature roars, green smoke pouring from where a head should be. It runs off towards the city, leaving destruction in it's wake.
He chuckles. "If that doesn't give them a good smack in the pants, then i'll have to make something myself."

The creature arrives in the city and roars, bashing down the gates and ducking to get inside. It starts says "I CHALLENGE ANYONE THAT DARES FIGHT THE BEHEMOTH. FIGHT ME TO THE DEATH!"