An Alpha's blood is one of the three bloods the Winchesters needed to construct their anti-Leviathan weapon. They used the Alpha Vampire's blood, since he is the only known alpha left, and thus, a Father of Fallen Beasts.
The Winchesters learn from the Leviathan tablet that as part of the weapon to defeat the Leviathans, they need the blood of the "Father of Fallen Beasts." Bobby Singer realizes that this means they need the blood of an Alpha and Crowley points them towards the Alpha Vampire who escaped his prison before Castiel destroyed it and the monsters inside. Locating the Alpha Vampire with the help of Emily, the Winchesters try to convince him to give them his blood as they have a common enemy in the Leviathans. The Alpha Vampire refuses as he believes that he and the Leviathans are on the same side, but after an attack by Edgar, he realizes the truth and agrees to give the Winchesters his blood without a fight. The Alpha Vampire fills a glass with his blood and lets the Winchesters leave with one of his kidnapped children, Allan and the blood though neither side are happy about letting the other live.
After getting the blood along with the Fallen Angel's blood and Ruler of Hell's blood they need, the Winchesters mix the three bloods together and pour it over the bone of Sister Mary Constant and are worried when nothing happens. However, the weapon they create with the help of the Alpha blood works and Dick Roman is killed by it, defeating the Leviathans.
- Season 6