The Inferno, Canto 21 (source)

Vio-lances are wicked hell weapons. They usually look like large spears or halberds, with purple-tinged blades of unknown (and seemingly indestructible) metal. Holy magic does not function within throwing range of a vio-lance. If a death blow is struck with a vio-lance, the victim explodes messily, showering all nearby with gore, and making any attempt at resurrection futile.