Grand Marshal Skaldak is the main antagonist of the Doctor Who episode "Cold War". He is a member of the Ice Warriors, and was, according to the Eleventh Doctor, the greatest hero the Martian race ever produced.
He commanded a fleet called the Nix-Thassis, with his daughter beside him. The Doctor also claimed that his foes honored him so much they carved his name into their flesh just before they died.
Eventually, he wound up frozen in the ice at the Earth's North Pole around 3,000 BC. 5,000 years later in 1983, Soviet scientist Professor Grisenko found him.
Impatient enough to not wait until returning to Moscow, Piotr, a crew member of the Firebird, thawed Skaldak with a blowtorch. Disorientated from the sudden awakening, Skaldak went on a brief rampage that caused the submarine to begin to sink. After the Doctor saved the Firebird by guiding it to an underwater ridge, Skaldak was knocked out and captured, and later learnt how long he been in the ice, which sent him into a state of grief. This was exacerbated when he attempted to contact his fellow Ice Warriors, but they didn't respond.
Feeling he had nothing left to lose, he left his armour to learn more about the submarine and the humans. As soon as he learned about the nuclear missiles on board, he decided to fire them and wipe out humanity as payback for attacking him.
However, just as he was about to fire them, another encounter with the Doctor made him hesitate, and the Doctor's companion, Clara Oswald, appealed to the memory of Skaldak's daughter to make him stop.
Moments later, a spaceship belonging to Skaldak's fellow Ice Warriors arrived to rescue him. He left on the spaceship, and deactivated the warheads as a final show of mercy before he left Earth
Personality and Characteristics
Like most Ice Warriors, Skaldak was honorable but when he was desperate he threw away his honor and started crawling around the submarine out of his armor, something that was considered highly dishonorable among the Ice Warriors. Believing that he was the last of his kind, Skaldak decided that honor didn't matter any more and devoted himself to getting revenge instead. He was ferocious in battle, and his reputation was legendary; it was said that his victims carved his name into their skin before they died. He tore most of his victims to pieces in the submarine in order to learn more about human physiology and judging by his opprobrious reputation, it appeared that he was also slightly sadistic and manipulative.
However, Skaldak did have a sensitive and sentimental side. He was upset by the death of his daughter and in honor of her memory, he stopped his murderous rampage, after Clara reminded him that if he went through with his plan he would cause other people to go through the same pain he'd suffered when he lost his family. Skaldak showed his honor and mercy by deactivating the warheads before he left Earth, having originally intended to use them to start another World War. He also showed respect to fellow warriors, even if they were his enemies, and complimented the Captain on his strategy of negotiating "from a position of strength".