The West African Gaboon viper has a bite that causes blood to congeal so that prey die from masses of blood clots.
Blood toxins are found in the lance-headed snakes of South America and in the Gaboon viper, among others. These large and powerful snakes' venom can work in two different—but similarly deadly—ways.
The venom can function as a specialized cell toxin that very specifically
targets the prey's red blood cells and destroys blood vessels. The animal then dies of internal and external bleeding. Or the blood toxin can speed up coagulation, so that blood clots throughout the prey's body. This way is especially fast-acting.