Arzeth the Merciless is a leader of fiends and a minion of Illidan. He is also a minor villain in the Warcraft universe. Arzeth led an attack on a Broken temple and enslaved the citizens. He then ordered his new slaves to dig up an ancient crystal said to be beneath the temple ruins.
When one of the Broken slaves escaped him, they put a plan together to stop Arzeth. They hired an adventurer to slay his minions and free the slaves, where they then freed the remains of his slaves.
The final stage of the plan was to recover artifacts from within the temple to reassemble a staff that could weaken him. When used on him, he shrunk in size and his physcial strength decreased. He still tried to kill the adventurer, but was slain in the battle.