A rock-like Excalbian who recreates historical figures to fight Kirk and Spock in a test of good and evil in The Savage Curtain.
Yarnek is an Excalbian, a being of living rock from the molten planet Excalbia. In The Savage Curtain, the Excalbians want to understand the human ideas of good and evil, so Yarnek recreates figures from history and pits them against each other.
Yarnek places Kirk and Spock alongside Abraham Lincoln and Surak against a team of notorious villains, among them Colonel Green and Kahless. He promises that the winners will live. When the villains flee, Yarnek concedes he has learned little from the experiment and releases the Enterprise.