“Sources confirm that Team Darlton is looking to introduce two new
characters this season – and they’re both as mysterious as they are
lethal. They’re also coming in as recurring players with an option to
become series regulars in Season 6.”
[CAESAR] 35-45. He is dangerous, physical and extremely intelligent with a dark past. He is a mysterious man whose intentions are unclear. He can charm us or kill us…Recurring guest star with possible series option for season 6.
[ILANNA] 25-35. She is a European woman of great intelligence, powerful and charming yet incredibly dangerous, too. She is alluring and very used to getting her own way. Her past is deeply mysterious and dark… Recurring guest star with possible series option for season 6.
Source: Ausiello @ EW