Within the clans of the Beyond, certain wolves were selected at a very young age to train for Blood Watch.
The Blood Watch is first mentioned in the chapter "Secrets of the Gadderheal." Finbar Fengo was talking to Edme and Faolan about if they found anything while they were scouting and he then asked them if they would go to the MacDuncan clan and see why Liam MacDuncan was wandering off and why he wasn't rotating the Blood Watch.
After Edme and Faolan rested, they headed toward the MacDuncan clan and after they talk to Liam they take Mhairie and Dearlea and head toward the Blood Watch. Later, while the four wolves are going to the Blood Watch, Faolan and Edme talk about which wolves are going to die from the famine first and then they decide to round up all of their old gnaw wolf friends as possible and take them to the Blood Watch with them. They go get Tearlach only to find out that he has died. Then they run into the Whistler and take him with them. When they got to the Blood Watch they started serving immediately.
Later the five wolves go off to try to break up a Skaars circle and are unsuccessful, when they get back to the Blood Watch they see strange lights in the sky and hear the skreeleens howling in confusion. Faolan and Edme went to talk to the Blood Watch captain, Tamsen, about their idea of getting all the gnaw wolves and bringing them to the Blood Watch and she sends scouts out to do so.
The Whistler made himself invaluable as a skreeleen, alerting the other blooders about any outclanners that have slipped the boarder. He was a lieutenant and there was talk about making him captain. When the strange lights showed up, the other wolves howled in confusion but the Whistler didn't, and when pressed by Tamsen he replied, "They have no history. And there no way to interpret them as with the sky fire of summer storms. It would be dishonest for me to howl in complete ignorance." And Tamsen respected him for that
A few days later, Creakle, a gnaw wolf from the MacDuff clan, showed up and Edme and Faolan left to go to the Sark and Gwynneth at the Obea Tree. That was the last time the Blood Watch was ever mentioned.
The wolves of the Blood Watch hold the important duty of protecting the Beyond by keeping the savage outclanners out of the Beyond and in the Outermost. They are the Beyond's "border patrol".
There are about thirty cairns, each topped with a wolf looking over the border of the Beyond and the Outermost. If an outclanner was caught slipping the Beyond-Outermost border, then the blooders would immediately kill them or chase them out back to the Outermost.