Marius, also known as Old Marius and Marius the Fierce, is a recurring character in the sixth season. He is a sellsword and prominent member of the Midnight Sons, serving as Baelic's second-in-command. He has been a sellsword for over thirty years.
After Baelic and a third of the Midnight Sons desert following the death of Carmine Grayburn, Marius replaces Baelic as Captain of the Midnight Sons and also takes his place as a lieutenant within Grayburn's Legion. He is also shown to be the only one of Carmine's advisors, other than Taria Dresden, who is fully supportive of Dominick Dresden becoming the new High Commander.