It's traditionally made only when a pig is butchered for a ceremony — the sausage exists specifically because Igorot ritual slaughter produces blood that shouldn't go to waste.
Pig's blood is mixed with minced fat, ginger, garlic, and onion, then packed into cleaned intestine casings and boiled until set into a dark, dense sausage. Baguio restaurants specializing in Cordillera cuisine now serve it as a highland specialty for visitors.