Ed Appel was a male Human civilian in the 23rd century. In 2267, he was a high-ranking miner assigned as the chief processing engineer on the Janus VI colony. A purple uniform distinguished him from the other miners.
That same year, when a mysterious creature began killing miners, Appel was the only one to see it and live. He only got a glimpse of it, describing it as "big and shaggy", and even shot it, though his less effective phaser type-1 meant the creature escaped unharmed.
When James T. Kirk and Spock attempted to communicate with the injured Horta, Appel lead a number of riotous miners to the end of the tunnel, demanding to approach and kill the creature. After being ordered to remain in their place by Security Chief Giotto, Appel and the other colonists attacked the security officers. Upon reaching the chamber, Kirk handed Appel their stolen circulating pump and informed them of the potential new arrangement between the Horta and the miners. (TOS: "The Devil in the Dark")
Appel was played by Brad Weston.
His character was described in the script as "a tough looking, squat, business-like man of middle age, with a phaser #1 on his belt".