Rigg will appear with her daughter Rachael Stirling in the Mark Gatiss-penned 'The Crimson Horror', which will centre on a mother and daughter harbouring a dark secret.
Speaking to Vulture, Coleman offered the first hints on what fans can expect from Rigg's guest appearance.
"Oh my God, she was so funny on set. She's got a lot of banter on her," Coleman declared. "I think [co-star Matt Smith] described her role as an old hag - but in the best possible way."
Coleman added of 'The Crimson Horror's storyline: "She's our villain and she runs a place in 1800 Yorkshire called Sweetville, which is kind of Stepford Wives-y. She has a big factory and she's up to no good.
"Her daughter, Rachael Stirling, is also playing her daughter on the show, and they just go at each other.