Giselher (d. September 1267) was the ringleader of the Rats. At one point, while incredibly drunk, he got drafted into an unknown army but was so drunk he couldn't even remember which one but sobered up enough after a thrashing and deserted, taking to the woods.
Soon enough he formed a gang with other deserters and fugitives in the area and they started ransacking and burning to the ground villages and ambushing the Nilfgaardian Army until one day the group mistakenly wandered too close to a group of elves in the forest, who rained lethal arrows down on the group. Giselher ended up getting pinned to a tree but survived while the rest died. The next morning Iskra, an elven woman banished by her own people, found and freed him and they became traveling companions and later lovers.
They then met Asse, Kayleigh, Reef, and Mistle during the holiday of Lammas in Geso and formed a gang. The entire gang then, with the exception of Ciri, was killed at the hands of Leo Bonhart in Jealousy.