Fek'Ihri

From Memory Alpha, the free Star Trek reference.

The Fek'Ihri were an ancient enemy of Kahless the Unforgettable on Qo'noS 1,500 years ago, when he was building the Klingon Empire. Kahless conquered the Fek'Ihri wielding the Sword of Kahless, the first bat'leth. (DS9: "The Sword of Kahless")

It is unknown if there is an etymological or mythological relationship between the Fek'Ihri and Fek'lhr, the hideous guardian of the gates of Gre'thor.