The Nissir gang was the baron Lutz's militia near the border of Geso. The gang, referred to as "the minions of the law" by the baron, was known for raping women and killing cattle which greatly contributed to the fear they inspired in Nilfgaardian citizens. The leader of the gang was Vercta. He met with his friend, Skomlik, the leader of the Trappers and together they coordinated their respective gangs' efforts.
Baron Lutz of Tyffi had ordered the Nissir gang to capture the Rats, yet another gang. In particular, they captured Kayleigh and were in the process of bringing him back to Tyffi to be punished for robbing one of Lutz's administrators. Meanwhile, Ciri was captured by Trappers. Both gangs met up at the inn in Glyswen with their prisoners.
It was at the inn that Ciri helped Kayleigh escape by taking knife from the Innkeeper and cutting his bonds. Vercta's group was slaughtered by Rats who also showed up to rescue Kayleigh.