Krell was the Klingon warrior who, in 2268 was responsible for upsetting the balance of power on the planet Neural by providing a rival clan of villagers led by Apella with the "advanced technology" of flintlock weapons.
He promised Apella that if he cooperated with the Klingons, he would be given power over the planet. In turn, Krell would be able to establish a puppet government with alliance to the Klingon Empire. Krell's mission was foiled when James T. Kirk discovered the plot and armed Tyree's clan with the same weapons. (TOS: "A Private Little War")
Background information Edit
Krell was played by actor Ned Romero.
The original script for the episode featured Kor instead of Krell, however, associate producer Robert Justman objected against the frequent use of the character, noting that in such a big galaxy, it'd be highly unlikely for Kirk to bump into "good old Kor" every time the Enterprise encounters with Klingons. (At that time, Kor was due to appear in "The Trouble with Tribbles", however, John Colicos later turned out unavailable to reprise the role.) (These Are the Voyages: TOS Season Two)
Of particular behind-the-scenes interest is that Krell's darkened complexion and upswept, bushy eyebrows represent a return to the original Klingon makeup design used on Kor and his men in the first season's "Errand of Mercy", and later on Kang, Kahless and all other Klingons in the third season. For some reason, at the beginning of season two, the Klingons Kras (TOS: "Friday's Child") and Koloth, Korax, and their men (TOS: "The Trouble with Tribbles") were styled with Caucasian skin and Human-style eyebrows.