The 43-year-old actress True Blood star is to join The CW drama's second season, reported Digital Spy.
Porter will take on the role of Indra, a Grounder warrior.
Her character is described as both regal and experienced.
The actress has previously appeared on the network in 'The Vampire Diaries' and 'Ringer'.
Porter is best known for her role as Lettie Mae Thornton in 'True Blood'. The hit HBO series recently ended after seven seasons this past August.