Gambler

Gamblers are two or three hostile Nord NPC's encountered in Cragslane Cavern, just south of Shor's Stone.

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Gamblers are not very hard to kill, it taking only five or six hits because they do not have armor on, and become hostile on sight, and are accompanied by the higher-level Cragslane's barkeep, Bartend. They may wield any number of iron and steel weapons, including war axes, maces, and swords. The boss in his study to the left, Butcher, will not notice that you are fighting the gamblers unless you run into his study with them on your tail. When you come in they may be routing for pit wolves or having a drink of mead, courtesy of Bartend.

Becoming Thane of Riften
The Dragonborn must kill everyone in the cavern to become Thane of Riften, because they sell Skooma and Moon Sugar to Sarthis Idren and Orini Dral in the Riften Warehouse, and must be eliminated to save Wujeeta and other citizens.