Frost, who will be seen as Santa in next month's episode following his surprise cameo at the end of Series 8 finale Death in Heaven, said to TV & Satellite Week:
"I wanted to make him slightly edgy and cross at times and a bit like a gangster.The magazine's preview of the Christmas special also names the monsters which will appear during the episode:
"I want viewers to be kept in the dark as to his intentions, so you don't know if he's good or if he's evil."
The Doctor and Clara are called into action when the crew of a polar base come under attack from a mysterious band of new villains known as the Sleepers and the Dream Crabs.Last Christmas - which has already received a teaser trailer and preview clip - will air on Christmas Day on BBC One with a provisional timeslot of 6:15pm.
Before then, however, we're currently holding our very own Christmas Cup to determine your favourite Christmas special, so don't forget to vote in our knockout quarter-finals!
[Source: Doctor Who TV]