Commander Kruge
Commander Kruge was the commanding officer of a Klingon Bird-of-Prey during the late 23rd century. He was also the lover of the Klingon spy Valkris and had a pet monster dog.
In 2285, after receiving intelligence on the powerful Genesis Device from the freighter Merchantman, Kruge took his ship and crew to the Genesis Planet in a rogue operation aimed at stealing the technology, which he perceived as a weapon. Upon entering Genesis orbit, Kruge ordered a deadly attack on the Federation science vessel USS Grissom, killing the entire crew, save Genesis scientist David Marcus and Lieutenant Saavik, who were on the Genesis Planet conducting a survey mission. His intent, however, was not to kill the crew; he only ordered their engines targeted, so that he could get information from them. He promptly executed the officer that hit the "lucky shot". Later in the Genesis incident, he ordered the execution of one of the prisoners as "enemies of galactic peace". As the Klingon crewman started to stab Saavik with his dagger from behind her James T. Kirk's son, David Marcus stepped in to stop him and ended up being stabbed in the chest in short order instead. Afterwords, the Klingon held his communicator in front of her so she could report the news to Admiral Kirk. This devastated him beyond measure which would haunt him for years afterward. In the novelization of Star Trek III, David and Saavik become lovers...which possibly explains why he steps in to stop the Klingon from killing her.
Kruge intended to seize control of the USS Enterprise following an attack on the Federation starship which left the vessel disabled. However, Admiral Kirk thought ahead of Kruge, beamed his crew down to Genesis and lured his boarding party aboard the Enterprise with the auto destruct sequence armed. When Kruge's officers informed their captain of the mysterious countdown taking place on the bridge, Kruge tried to warn them off the ship, but, it was too late and the Enterprise exploded, killing Kruge's men in the process.
Kruge falls to his death
On the surface of the Genesis planet, Kruge tried to thwart Federation Rear Admiral Kirk's attempts to secure the body of Captain Spock and tried to bargain Spock's revived body for the Genesis technology. As the Genesis planet began to break up, Kruge fought Kirk in a lengthy fistfight, and was killed after Kirk kicked him into a sea of lava. (Star Trek III: The Search for Spock)
The following year, the Klingon Empire demanded that the Federation Council extradite Kirk for the deaths of Kruge and most of his crew. The Council denied this request. (Star Trek IV: The Voyage Home)
Background
Kruge was played by actor Christopher Lloyd (although Edward James Olmos of Battlestar Galactica fame had also auditioned for the role). [1] The stop-motion puppet of Kruge's fall from the precipice, following his defeat with Kirk, was animated by Tom St. Armand and Dennis Muren.
According to the script, Kruge was described as a "Battle Commander" and was "a Klingon War Lord of handsome but frightening presence, and relative youth." This explains why Saavik, Valkris and his crew referred to him as "my Lord."
Kruge was the second Klingon to try and seize control of the Enterprise with Kang being the first. (TOS: "Day of the Dove")
The scene of Kruge falling from the precipice was shown during the viseo montage at the end of the Star Trek 25th Anniversary Special, followed by the text "He Boldly Went Where Noone Went Before."