Introduced in Cursor's Fury as a Knight in the First Aleran, Crassus is initially at odds with Max and Tavi. We eventually learn that Max's scars are a result of beatings he took for things Crassus had actually done. Eventually the two brothers reconcile and we later discover that they actually both manifest similar Water Furies in the shape of lions. When Tavi ascends to Captain of the First Aleran Legion, he promotes Crassus to the rank of Knight Tribune. Later, when Tavi is arrested by Senator Arnos, he puts Crassus in command of the Legion. He works as a capable Tribune under Tavi throughout the Vord war. In the Vord Queen's assault on Tavi, he is gravely injured and although healed by his mother, he never fully recovers, thus having to leave the legion. He still bears a grudge against Tavi afterwards for not telling him his mother was alive, straining their friendship.
As the son of the High Citizenry, Antillus Crassus demonstrates ability in all crafting disciplines, Water, Wind, Earth, Fire and Metal. His water fury manifests as a great lion, as does his half-brother's.