The Karrans are a primitive Human race in the Pegasus galaxy, from the planet Karra. They are allied with the Wraith, but despite this, the Tau'ri of the Atlantis expedition insist they watch over them. (SGA: "Wraithfall 3")
Despite the Karrans being content with their arrangement with the Wraith, Major John Sheppard, Aiden Ford, and the Atlantis expedition intervened and drove the Wraith from their base of operations in an Experimental laboratory on Vohl. An act which was criticized by both the Wraith and the Karran Honored One Dakh. (SGA: "Wraithfall 3")
The Karrans perform a ritual every three months known as Wraithfall. This is a deal with the Wraith, where they offer five of their people to them. Those selected are then considered an Honored One and are given a Holy medallion of Karra. They're then taken into a Wraith Dart. This act is considered a happy occasion.
The time spent in between cullings, where the Wraith don't show up, is sad for the Karrans, as they miss performing the ritual. Without it, their culture feels unmoored and adrift to them. (SGA: "Wraithfall 1")