After last canto's disquisition on sin, Canto 12 picks up the action. Sidling past the Minotaur (I love all the monsters!), Dante & Virgil come to a vast, boiling stream of blood: the River Phlegethon. Centaurs ring the strand, firing arrows at bobbing souls of the violent. Virgil enlists one to ford the river with Dante on its back (remember, Virgil is insubstantial & needs no help). How are the violent distinct from the wrathful of Circle #4, swimming in the Styx? It's more than mere degree: here are tyrants like Alexander and Attila along with career criminals.