Former Lost and Revolution star Elizabeth Mitchell is the latest actor to join Disney fantasy Once Upon a Time.

Mitchell’s character is being kept under wraps but according to Entertainment Weekly she is expected to play a villainous role associated with incoming Frozen sisters Anna (Elizabeth Lail) and Elsa (Georgina Haig).

Lail and Haig were recently confirmed as new cast members for season four, alongside Greek actor Scott Michael Foster, who will appear as down-to-earth hero Kristoff.

Once Upon a Time already features the likes of Robert Carlyle, Emilie de Ravin and Lana Parilla, as well as Irish pair Sarah Bolger and Colin O'Donoghue.

Mitchell is due to play a recurring role in the upcoming fourth season, which premieres on ABC in the US in September and will follow on RTÉ One.

The actress most recently starred in NBC's post-apocalyptic sci-fi thriller Revolution, until it was cancelled in May after a two-season run. She previously appeared in Lost and V.