The Snape Viper was a repeating crossbow designed by Tobias Luca Snape and Eileen Valora Prince. Tobias had the main plans for it saved for years in his vault in Gringotts, and finally delivered a group of them along with the plans to Hogwarts through the floo system. "In case you're in a place where wands won't work, you'll need these."- Tobias The crossbow was an extremely swift weapon, using its own recoil to cock itself.